C语言前缀表达式转后缀

将前缀表达式从右往左遍历，遇到操作数就直接输出到后缀表达式中，遇到运算符则将其压入栈中，等到遇到下一个操作数时，将栈顶运算符取出与该操作数和前面的运算符进行运算，将结果输出到后缀表达式中。最后将栈中的所有运算符依次弹出并输出到后缀表达式中即可。

以下是 C 语言代码实现：

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

#define MAX_STACK_SIZE 100

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

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

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

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

void prefix_to_postfix(char *prefix, char *postfix) {
    Stack stack;
    stack.top = -1;
    int len = strlen(prefix);
    for (int i = len - 1; i >= 0; i--) {
        if (is_operator(prefix[i])) {
            char op1 = pop(&stack);
            char op2 = pop(&stack);
            postfix[strlen(postfix)] = op1;
            postfix[strlen(postfix)] = op2;
            postfix[strlen(postfix)] = prefix[i];
            push(&stack, postfix[strlen(postfix) - 1]);
        } else {
            push(&stack, prefix[i]);
        }
    }
    while (stack.top != -1) {
        postfix[strlen(postfix)] = pop(&stack);
    }
    postfix[strlen(postfix)] = '\0';
}

int main() {
    char prefix[100], postfix[100] = "";
    printf("Enter prefix expression: ");
    gets(prefix);
    prefix_to_postfix(prefix, postfix);
    printf("Postfix expression: %s", postfix);
    return 0;
}