c语言将运算表达式转化为后缀式表达式的代码

以下是将运算表达式转化为后缀式表达式的C语言代码：

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

#define MAX_SIZE 100

typedef struct {
    char data[MAX_SIZE];
    int top;
} Stack;

void init_stack(Stack *s) {
    s->top = -1;
}

void push(Stack *s, char c) {
    if (s->top == MAX_SIZE - 1) {
        printf("Stack overflow\n");
        exit(1);
    }
    s->top++;
    s->data[s->top] = c;
}

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

int is_operator(char c) {
    return (c == '+' || c == '-' || c == '*' || c == '/');
}

int precedence(char c) {
    if (c == '+' || c == '-') {
        return 1;
    } else if (c == '*' || c == '/') {
        return 2;
    } else {
        return 0;
    }
}

void infix_to_postfix(char infix[], char postfix[]) {
    Stack s;
    init_stack(&s);
    int i = 0, j = 0;
    while (infix[i] != '\0') {
        char c = infix[i];
        if (isdigit(c)) {
            postfix[j] = c;
            j++;
        } else if (is_operator(c)) {
            while (s.top != -1 && is_operator(s.data[s.top]) && precedence(s.data[s.top]) >= precedence(c)) {
                postfix[j] = pop(&s);
                j++;
            }
            push(&s, c);
        } else if (c == '(') {
            push(&s, c);
        } else if (c == ')') {
            while (s.top != -1 && s.data[s.top] != '(') {
                postfix[j] = pop(&s);
                j++;
            }
            if (s.top == -1) {
                printf("Unmatched parenthesis\n");
                exit(1);
            }
            pop(&s);
        } else {
            printf("Invalid character\n");
            exit(1);
        }
        i++;
    }
    while (s.top != -1) {
        if (s.data[s.top] == '(') {
            printf("Unmatched parenthesis\n");
            exit(1);
        }
        postfix[j] = pop(&s);
        j++;
    }
    postfix[j] = '\0';
}

int main() {
    char infix[MAX_SIZE], postfix[MAX_SIZE];
    printf("Enter infix expression: ");
    fgets(infix, MAX_SIZE, stdin);
    infix_to_postfix(infix, postfix);
    printf("Postfix expression: %s\n", postfix);
    return 0;
}

使用方法：

1. 编译代码：

   gcc -o postfix postfix.c

2. 运行程序：

   ./postfix

3. 输入中缀表达式，按回车键：

   Enter infix expression: (3+4)*5-6/2

4. 程序输出后缀表达式：

   Postfix expression: 34+5*62/-