update,

marissa.sam/task2/temp/_draft/helloworld copy 2.cpp

@@ -0,0 +1,123 @@
+#include <iostream>
+#include <stack>
+#include <cctype>
+#include <cstring>
+
+// 1. how to read and store the input?
+std::string readInput()
+{
+    std::string input;
+    char c;
+    while (std::cin.get(c)) {
+        if (c == '\n')
+            break;
+        input += c;
+    }
+    return input;
+}
+
+// 2. pseudo code of the algorithm
+// convert to postfix expression use stack, 
+// 1. if it is an operand, push it into stack, 
+// 2. if it is an operator,  pop the top two elements and push the operator result, 
+// 3. if it is a bracket, pop until the matched bracket, then push it into stack, 
+// 4. if the input is end, pop all the remaining elements, 
+// 5. if the last element is a bracket, return error, 
+// else return the result
+std::string infixToPostfix(const std::string& input)
+{
+    std::stack<char> stack;
+    std::string postfix;
+    const char* precedence = "+-*/()";
+    for (const auto& c : input) {
+        if (std::isalpha(c) || std::isdigit(c)) {
+            postfix += c;
+        } else if (c == '(') {
+            stack.push(c);
+        } else if (c == ')') {
+            while (!stack.empty() && stack.top() != '(') {
+                postfix += stack.top();
+                stack.pop();
+            }
+            if (!stack.empty()) {
+                stack.pop();
+            }
+        } else {
+            while (!stack.empty() && precedence[c] <= precedence[stack.top()]) {
+                postfix += stack.top();
+                stack.pop();
+            }
+            stack.push(c);
+        }
+    }
+    while (!stack.empty()) {
+        postfix += stack.top();
+        stack.pop();
+    }
+    return postfix;
+}
+
+// 3. data structures used in the algorithm
+// stack
+// string
+
+// 4. time complexity
+// O(n), where n is the length of input
+
+// 5. space complexity
+// O(n), where n is the length of input
+
+// 6. how to store the postfix expression?
+// using string
+
+int main()
+{
+    std::string input = readInput();
+    std::string postfix = infixToPostfix(input);
+    std::cout << postfix << std::endl;
+
+    // 1. how to read the postfix expression
+    // read postfix expression from standard input stream and store them into string
+
+    // 2. pseudo code of the algorithm
+    // evaluate a postfix expression use stack, 
+    // if it is an operand, push it into stack, 
+    // if it is an operator, pop the top two elements, apply the operator, and push the result, 
+    // if it is a bracket, pop until the matched bracket, then push it into stack, 
+    // if the input is end, return the last element in stack, 
+    // else error
+    std::stack<int> stack;
+    const char* operators = "+-*/";
+    for (const auto& c : postfix) {
+        if (std::isalpha(c) || std::isdigit(c)) {
+            stack.push(c - '0');
+        } else if (std::strchr(operators, c)) {
+            int operand2 = stack.top();
+            stack.pop();
+            int operand1 = stack.top();
+            stack.pop();
+
+            switch (c) {
+            case '+':
+                stack.push(operand1 + operand2);
+                break;
+            case '-':
+                stack.push(operand1 - operand2);
+                break;
+            case '*':
+                stack.push(operand1 * operand2);
+                break;
+            case '/':
+                stack.push(operand1 / operand2);
+                break;
+            default:
+                return -1;
+            }
+        } else {
+            return -1;
+        }
+    }
+    std::cout << stack.top() << std::endl;
+
+    return 0;
+}

marissa.sam/task2/temp/_draft/helloworld copy 3.cpp

@@ -0,0 +1,121 @@
+#include <iostream>
+#include <stack>
+#include <string>
+#include <cctype>
+#include <map>
+
+// Function to convert infix expression to postfix expression
+std::string infixToPostfix(const std::string &infix)
+{
+    std::stack<char> s;
+    std::string postfix;
+    std::map<char, int> precedence = {{'+', 1}, {'-', 1}, {'*', 2}, {'/', 2}, {'(', 0}};
+
+    for (char c : infix)
+    {
+        if (std::isalnum(c))
+        { // 1. if operand, add to postfix
+            postfix += c;
+        }
+        else if (c == '(')
+        { // 2. if '(', push to stack
+            s.push(c);
+        }
+        else if (c == ')')
+        { // 3. if ')', pop until '('
+            while (!s.empty() && s.top() != '(')
+            {
+                postfix += s.top();
+                s.pop();
+            }
+            if (!s.empty())
+                s.pop(); // pop '('
+        }
+        else
+        { // 4. if operator, pop operators with greater or equal precedence
+            while (!s.empty() && precedence[c] <= precedence[s.top()])
+            {
+                postfix += s.top();
+                s.pop();
+            }
+            s.push(c); // push current operator
+        }
+    }
+    // 5. pop remaining operators
+    while (!s.empty())
+    {
+        postfix += s.top();
+        s.pop();
+    }
+    return postfix;
+}
+
+// Function to evaluate postfix expression
+int evaluatePostfix(const std::string &postfix)
+{
+    std::stack<int> s;
+
+    for (char c : postfix)
+    {
+        if (std::isdigit(c))
+        { // 1. if operand, push to stack
+            s.push(c - '0');
+        }
+        else
+        { // 2. if operator, pop two operands, evaluate and push result
+            int op2 = s.top();
+            s.pop();
+            int op1 = s.top();
+            s.pop();
+            switch (c)
+            {
+            case '+':
+                s.push(op1 + op2);
+                break;
+            case '-':
+                s.push(op1 - op2);
+                break;
+            case '*':
+                s.push(op1 * op2);
+                break;
+            case '/':
+                s.push(op1 / op2);
+                break;
+            }
+        }
+    }
+    return s.top(); // 3. result is the only element in stack
+}
+
+int main()
+{
+    std::string infix;
+    // std::cout << "Enter an arithmetic expression: ";
+    // std::getline(std::cin, infix);
+
+    std::cout << "e.g. 1 1+4*5" << std::endl;
+    infix = "1+4*5";
+    std::string postfix = infixToPostfix(infix);
+    std::cout << "Postfix expression: " << postfix << std::endl;
+
+    int result = evaluatePostfix(postfix);
+    std::cout << "Result: " << result << std::endl;
+
+    std::cout << "e.g. 2 (1+4)*5" << std::endl;
+    infix = "(1+4)*5";
+    postfix = infixToPostfix(infix);
+    std::cout << "Postfix expression: " << postfix << std::endl;
+
+    result = evaluatePostfix(postfix);
+    std::cout << "Result: " << result << std::endl;
+
+    std::cout << "e.g. 3 1+4-5" << std::endl;
+    infix = "1+4-5";
+    postfix = infixToPostfix(infix);
+    std::cout << "Postfix expression: " << postfix << std::endl;
+
+    result = evaluatePostfix(postfix);
+    std::cout << "Result: " << result << std::endl;
+
+    return 0;
+}

marissa.sam/task2/temp/_draft/helloworld copy.cpp

@@ -0,0 +1,103 @@
+#include <iostream>
+#include <stack>
+#include <string>
+#include <cctype>
+#include <map>
+
+// Function to convert infix expression to postfix expression
+std::string infixToPostfix(const std::string &infix)
+{
+    std::stack<char> s;
+    std::string postfix;
+    std::map<char, int> precedence = {{'+', 1}, {'-', 1}, {'*', 2}, {'/', 2}, {'(', 0}};
+
+    for (char c : infix)
+    {
+        if (std::isalnum(c))
+        { // 1. if operand, add to postfix
+            postfix += c;
+        }
+        else if (c == '(')
+        { // 2. if '(', push to stack
+            s.push(c);
+        }
+        else if (c == ')')
+        { // 3. if ')', pop until '('
+            while (!s.empty() && s.top() != '(')
+            {
+                postfix += s.top();
+                s.pop();
+            }
+            if (!s.empty())
+                s.pop(); // pop '('
+        }
+        else
+        { // 4. if operator, pop operators with greater or equal precedence
+            while (!s.empty() && precedence[c] <= precedence[s.top()])
+            {
+                postfix += s.top();
+                s.pop();
+            }
+            s.push(c); // push current operator
+        }
+    }
+    // 5. pop remaining operators
+    while (!s.empty())
+    {
+        postfix += s.top();
+        s.pop();
+    }
+    return postfix;
+}
+
+// Function to evaluate postfix expression
+int evaluatePostfix(const std::string &postfix)
+{
+    std::stack<int> s;
+
+    for (char c : postfix)
+    {
+        if (std::isdigit(c))
+        { // 1. if operand, push to stack
+            s.push(c - '0');
+        }
+        else
+        { // 2. if operator, pop two operands, evaluate and push result
+            int op2 = s.top();
+            s.pop();
+            int op1 = s.top();
+            s.pop();
+            switch (c)
+            {
+            case '+':
+                s.push(op1 + op2);
+                break;
+            case '-':
+                s.push(op1 - op2);
+                break;
+            case '*':
+                s.push(op1 * op2);
+                break;
+            case '/':
+                s.push(op1 / op2);
+                break;
+            }
+        }
+    }
+    return s.top(); // 3. result is the only element in stack
+}
+
+int main()
+{
+    std::string infix;
+    std::cout << "Enter an arithmetic expression: ";
+    std::getline(std::cin, infix);
+
+    std::string postfix = infixToPostfix(infix);
+    std::cout << "Postfix expression: " << postfix << std::endl;
+
+    int result = evaluatePostfix(postfix);
+    std::cout << "Result: " << result << std::endl;
+
+    return 0;
+}

marissa.sam/task2/temp/build.sh

@@ -0,0 +1,9 @@
+#!/usr/bin/env bash
+
+set -ex
+
+g++ -o output helloworld.cpp
+
+echo "build done"
+
+./output

marissa.sam/task2/temp/helloworld.cpp

@@ -0,0 +1,185 @@
+#include <iostream>
+#include <stack>
+#include <string>
+#include <cctype>
+#include <map>
+
+// 2. pseudo code of the algorithm
+// convert to postfix expression use stack,
+// 1. if it is an operand, add to postfix,
+// 2. if it is an operator,
+//      2.1 if it is the first operator, push into `s` stack
+//      2.2 if `s` stack already got element, compare the weight of opreators
+//      2.3 pop `s` stack until the top most one got smaller precedence
+// 3. if it is a bracket, push into stack `s`,
+// 3. if it is a closing bracket, pop all element from `s` stack back to postfix,
+// else return the result
+
+// Function to convert infix expression to postfix expression
+std::string infixToPostfix(const std::string &infix)
+{
+    std::stack<char> s;
+    std::string postfix;
+    std::map<char, int> precedence = {{'+', 1}, {'-', 1}, {'*', 2}, {'/', 2}, {'(', 0}};
+
+    for (char c : infix)
+    {
+        if (std::isalnum(c))
+        { // 1. if operand, add to postfix
+            postfix += c;
+        }
+
+        // 其實括號入面同括號出面嘅數你當佢兩條式計就得
+        else if (c == '(')
+        { // 2. if '(', push to stack
+            s.push(c);
+        }
+
+        // 咁去呢度關括號呀嘛,
+        // 咁佢咪會由個 stack 嗰度 port 返曬啲operator出嚟囉, 變咗可以 14+5*
+        else if (c == ')')
+        { // 3. if ')', pop until '('
+            while (!s.empty() && s.top() != '(')
+            {
+                postfix += s.top();
+                s.pop();
+            }
+            if (!s.empty())
+                s.pop(); // pop '('
+        }
+        else
+        { // 4. if operator, pop operators with greater or equal precedence
+            while (!s.empty() && precedence[c] <= precedence[s.top()])
+            {
+                postfix += s.top();
+                s.pop();
+            }
+            s.push(c); // push current operator
+        }
+    }
+
+    // 5. pop remaining operators, LIFO
+    while (!s.empty())
+    {
+        postfix += s.top();
+        s.pop();
+    }
+
+    return postfix;
+}
+
+// Function to evaluate postfix expression
+
+// 2. pseudo code of the algorithm
+// evaluate a postfix expression use stack,
+// if it is an operand, push it into stack,
+// if it is an operator, pop the top two elements, apply the operator, and push the result,
+// if it is a bracket, pop until the matched bracket, then push it into stack,
+// if the input is end, return the last element in stack,
+// else error
+
+int evaluatePostfix(const std::string &postfix)
+{
+    std::stack<int> s;
+
+    for (char c : postfix)
+    {
+        if (std::isdigit(c))
+        { // 1. if operand, push to stack
+            s.push(c - '0');
+        }
+        else
+        { // 2. if operator, pop two operands, evaluate and push result
+            int op2 = s.top();
+            s.pop();
+            int op1 = s.top();
+            s.pop();
+            switch (c)
+            {
+            case '+':
+                s.push(op1 + op2);
+                break;
+            case '-':
+                s.push(op1 - op2);
+                break;
+            case '*':
+                s.push(op1 * op2);
+                break;
+            case '/':
+                s.push(op1 / op2);
+                break;
+            }
+        }
+    }
+    return s.top(); // 3. result is the only element in stack
+}
+
+int main()
+{
+    std::string infix;
+    // std::cout << "Enter an arithmetic expression: ";
+    // std::getline(std::cin, infix);
+
+    // --- part 2 iteration:
+    // 1,4,5,*,+
+    // 1,20,+
+    // 21
+    std::cout << "e.g. 1 1+4*5" << std::endl;
+    infix = "1+4*5";
+    std::string postfix = infixToPostfix(infix);
+    std::cout << "Postfix expression: " << postfix << std::endl;
+
+    int result = evaluatePostfix(postfix);
+    std::cout << "Result: " << result << std::endl;
+
+    // --- part 2 iteration:
+    // 1,4,+,5,*
+    // 5,5,*
+    // 25
+    std::cout << "e.g. 2 (1+4)*5" << std::endl;
+    infix = "(1+4)*5";
+    postfix = infixToPostfix(infix);
+    std::cout << "Postfix expression: " << postfix << std::endl;
+    result = evaluatePostfix(postfix);
+    std::cout << "Result: " << result << std::endl;
+
+    // --- part 2 iteration:
+    // 1,4,+,5,-
+    // 5,5,-
+    // 0
+    std::cout << "e.g. 3 1+4-5" << std::endl;
+    infix = "1+4-5";
+    postfix = infixToPostfix(infix);
+    std::cout << "Postfix expression: " << postfix << std::endl;
+    result = evaluatePostfix(postfix);
+    std::cout << "Result: " << result << std::endl;
+
+    // --- part 2 iteration:
+    // 1,4,5,*,+,5,*
+    // 1,20,+,5,*
+    // 21,5,*
+    // 105
+    std::cout << "e.g. 4 (1+4*5)*5" << std::endl;
+    infix = "(1+4*5)*5";
+    postfix = infixToPostfix(infix);
+    std::cout << "Postfix expression: " << postfix << std::endl;
+
+    result = evaluatePostfix(postfix);
+    std::cout << "Result: " << result << std::endl;
+
+    // --- part 2 iteration:
+    // 1,4,5,*,+,2,5,*,-
+    // =>1,20,+,2,5,*,-
+    // =>21,2,5,*,-
+    // =>21,10,-
+    // =>11
+    std::cout << "e.g. 5 (1+4*5)-2*5" << std::endl;
+    infix = "(1+4*5)-2*5";
+    postfix = infixToPostfix(infix);
+    std::cout << "Postfix expression: " << postfix << std::endl;
+
+    result = evaluatePostfix(postfix);
+    std::cout << "Result: " << result << std::endl;
+
+    return 0;
+}

marissa.sam/task2/temp/main.cpp

@@ -0,0 +1,185 @@
+#include <iostream>
+#include <stack>
+#include <string>
+#include <cctype>
+#include <map>
+
+// 2. pseudo code of the algorithm
+// convert to postfix expression use stack,
+// 1. if it is an operand, add to postfix,
+// 2. if it is an operator,
+//      2.1 if it is the first operator, push into `s` stack
+//      2.2 if `s` stack already got element, compare the weight of opreators
+//      2.3 pop `s` stack until the top most one got smaller precedence
+// 3. if it is a bracket, push into stack `s`,
+// 3. if it is a closing bracket, pop all element from `s` stack back to postfix,
+// else return the result
+
+// Function to convert infix expression to postfix expression
+std::string infixToPostfix(const std::string &infix)
+{
+    std::stack<char> s;
+    std::string postfix;
+    std::map<char, int> precedence = {{'+', 1}, {'-', 1}, {'*', 2}, {'/', 2}, {'(', 0}};
+
+    for (char c : infix)
+    {
+        if (std::isalnum(c))
+        { // 1. if operand, add to postfix
+            postfix += c;
+        }
+
+        // 其實括號入面同括號出面嘅數你當佢兩條式計就得
+        else if (c == '(')
+        { // 2. if '(', push to stack
+            s.push(c);
+        }
+
+        // 咁佢呢度關括號呀嘛,
+        // 咁佢咪會由個 stack 嗰度 port 返曬啲operator出嚟囉, 變咗可以 14+5*
+        else if (c == ')')
+        { // 3. if ')', pop until '('
+            while (!s.empty() && s.top() != '(')
+            {
+                postfix += s.top();
+                s.pop();
+            }
+            if (!s.empty())
+                s.pop(); // pop '('
+        }
+        else
+        { // 4. if operator, pop operators with greater or equal precedence
+            while (!s.empty() && precedence[c] <= precedence[s.top()])
+            {
+                postfix += s.top();
+                s.pop();
+            }
+            s.push(c); // push current operator
+        }
+    }
+
+    // 5. pop remaining operators, LIFO
+    while (!s.empty())
+    {
+        postfix += s.top();
+        s.pop();
+    }
+
+    return postfix;
+}
+
+// Function to evaluate postfix expression
+
+// 2. pseudo code of the algorithm
+// evaluate a postfix expression use stack,
+// if it is an operand, push it into stack,
+// if it is an operator, pop the top two elements, apply the operator, and push the result,
+// if it is a bracket, pop until the matched bracket, then push it into stack,
+// if the input is end, return the last element in stack,
+// else error
+
+int evaluatePostfix(const std::string &postfix)
+{
+    std::stack<int> s;
+
+    for (char c : postfix)
+    {
+        if (std::isdigit(c))
+        { // 1. if operand, push to stack
+            s.push(c - '0');
+        }
+        else
+        { // 2. if operator, pop two operands, evaluate and push result
+            int op2 = s.top();
+            s.pop();
+            int op1 = s.top();
+            s.pop();
+            switch (c)
+            {
+            case '+':
+                s.push(op1 + op2);
+                break;
+            case '-':
+                s.push(op1 - op2);
+                break;
+            case '*':
+                s.push(op1 * op2);
+                break;
+            case '/':
+                s.push(op1 / op2);
+                break;
+            }
+        }
+    }
+    return s.top(); // 3. result is the only element in stack
+}
+
+int main()
+{
+    std::string infix;
+    // std::cout << "Enter an arithmetic expression: ";
+    // std::getline(std::cin, infix);
+
+    // --- part 2 iteration:
+    // 1,4,5,*,+
+    // 1,20,+
+    // 21
+    std::cout << "e.g. 1 1+4*5" << std::endl;
+    infix = "1+4*5";
+    std::string postfix = infixToPostfix(infix);
+    std::cout << "Postfix expression: " << postfix << std::endl;
+
+    int result = evaluatePostfix(postfix);
+    std::cout << "Result: " << result << std::endl;
+
+    // --- part 2 iteration:
+    // 1,4,+,5,*
+    // 5,5,*
+    // 25
+    std::cout << "e.g. 2 (1+4)*5" << std::endl;
+    infix = "(1+4)*5";
+    postfix = infixToPostfix(infix);
+    std::cout << "Postfix expression: " << postfix << std::endl;
+    result = evaluatePostfix(postfix);
+    std::cout << "Result: " << result << std::endl;
+
+    // --- part 2 iteration:
+    // 1,4,+,5,-
+    // 5,5,-
+    // 0
+    std::cout << "e.g. 3 1+4-5" << std::endl;
+    infix = "1+4-5";
+    postfix = infixToPostfix(infix);
+    std::cout << "Postfix expression: " << postfix << std::endl;
+    result = evaluatePostfix(postfix);
+    std::cout << "Result: " << result << std::endl;
+
+    // --- part 2 iteration:
+    // 1,4,5,*,+,5,*
+    // 1,20,+,5,*
+    // 21,5,*
+    // 105
+    std::cout << "e.g. 4 (1+4*5)*5" << std::endl;
+    infix = "(1+4*5)*5";
+    postfix = infixToPostfix(infix);
+    std::cout << "Postfix expression: " << postfix << std::endl;
+
+    result = evaluatePostfix(postfix);
+    std::cout << "Result: " << result << std::endl;
+
+    // --- part 2 iteration:
+    // 1,4,5,*,+,2,5,*,-
+    // =>1,20,+,2,5,*,-
+    // =>21,2,5,*,-
+    // =>21,10,-
+    // =>11
+    std::cout << "e.g. 5 (1+4*5)-2*5" << std::endl;
+    infix = "(1+4*5)-2*5";
+    postfix = infixToPostfix(infix);
+    std::cout << "Postfix expression: " << postfix << std::endl;
+
+    result = evaluatePostfix(postfix);
+    std::cout << "Result: " << result << std::endl;
+
+    return 0;
+}

marissa.sam/task2/temp/prompt.md

@@ -0,0 +1,31 @@
+# Task
+I want you to write a simple calculator to evaluate arithmetic expressions.
+Solve your problem step by step with C++.
+Please consider the precedence of operators as well.
+
+## It includes two parts:
+
+- In the first part, you need to convert the input to a postfix expression.
+- In the second part, you need to evaluate the postfix expression that you get in the first
+  part.
+- You need to implement your algorithms using c++.
+- You also need to write comment inside the code explaining the following items.
+
+## Part 1: Convert an expression to postfix expression using stack in STL
+
+1. how to read and store the input?
+2. pseudo code of the algorithm
+3. data structures used in the algorithm
+4. time complexity
+5. space complexity
+6. how to store the postfix expression?
+
+## Part 2: Use stack of STL to evaluate a postfix expression
+
+1. how to read the postfix expression
+2. pseudo code of the algorithm
+3. data structures used in the algorithm
+4. time complexity
+5. space complexity
+6. how to output the final result?
+