中缀表达式转换成后缀表达式并求值的c++代码

以下是中缀表达式转换成后缀表达式并求值的C代码：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>

#define STACK_SIZE 100

typedef struct {
    int top;
    int items[STACK_SIZE];
} Stack;

void push(Stack *s, int item) {
    if (s->top >= STACK_SIZE) {
        printf("Stack overflow\n");
        exit(1);
    }
    s->items[++(s->top)] = item;
}

int pop(Stack *s) {
    if (s->top <= -1) {
        printf("Stack underflow\n");
        exit(1);
    }
    return s->items[(s->top)--];
}

int priority(char operator) {
    switch(operator) {
        case '+':
        case '-':
            return 1;
        case '*':
        case '/':
            return 2;
        case '^':
            return 3;
        default:
            return 0;
    }
}

void infixToPostfix(char infix[], char postfix[]) {
    Stack s;
    s.top = -1;
    int i, j;
    for (i = 0, j = 0; infix[i] != '\0'; i++) {
        if (isdigit(infix[i])) {
            // operand
            postfix[j++] = infix[i];
        } else if (infix[i] == '(') {
            // left parenthesis
            push(&s, infix[i]);
        } else if (infix[i] == ')') {
            // right parenthesis
            while (s.items[s.top] != '(') {
                postfix[j++] = pop(&s);
            }
            pop(&s); // discard the left parenthesis
        } else {
            // operator
            while (s.top != -1 && s.items[s.top] != '(' && priority(infix[i]) <= priority(s.items[s.top])) {
                postfix[j++] = pop(&s);
            }
            push(&s, infix[i]);
        }
    }
    // pop any remaining operators from the stack
    while (s.top != -1) {
        postfix[j++] = pop(&s);
    }
    postfix[j] = '\0'; // terminate the postfix string
}

int evaluatePostfix(char postfix[]) {
    Stack s;
    s.top = -1;
    int i, op1, op2, result;
    for (i = 0; postfix[i] != '\0'; i++) {
        if (isdigit(postfix[i])) {
            // operand
            push(&s, postfix[i] - '0');
        } else {
            // operator
            op2 = pop(&s);
            op1 = pop(&s);
            switch (postfix[i]) {
                case '+':
                    result = op1 + op2;
                    break;
                case '-':
                    result = op1 - op2;
                    break;
                case '*':
                    result = op1 * op2;
                    break;
                case '/':
                    result = op1 / op2;
                    break;
                case '^':
                    result = 1;
                    for (int j = 0; j < op2; j++) {
                        result *= op1;
                    }
                    break;
            }
            push(&s, result);
        }
    }
    return pop(&s);
}

int main() {
    char infix[STACK_SIZE];
    char postfix[STACK_SIZE];
    printf("Enter an infix expression: ");
    scanf("%s", infix);
    infixToPostfix(infix, postfix);
    printf("Postfix expression: %s\n", postfix);
    printf("Result: %d\n", evaluatePostfix(postfix));
    return 0;
}

此代码实现了中缀表达式转换成后缀表达式并求值的功能。其中，`infixToPostfix()`函数将中缀表达式转换成后缀表达式，`evaluatePostfix()`函数对后缀表达式求值，`priority()`函数返回操作符的优先级，`push()`和`pop()`函数分别实现栈的入栈和出栈操作。在`main()`函数中，用户输入一个中缀表达式，程序将其转换成后缀表达式并输出，然后求出后缀表达式的值并输出。