后缀表达式求值C语言

以下是C语言实现后缀表达式求值的代码示例：

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

#define MAX_STACK_SIZE 100

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

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

int is_empty(Stack *s) {
    return s->top == -1;
}

int is_full(Stack *s) {
    return s->top == MAX_STACK_SIZE - 1;
}

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

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

int evaluate_postfix(char *expr) {
    Stack s;
    init(&s);

    for (int i = 0; expr[i] != '\0'; i++) {
        if (isdigit(expr[i])) {
            push(&s, expr[i] - '0');
        } else {
            int op1 = pop(&s);
            int op2 = pop(&s);
            switch (expr[i]) {
                case '+':
                    push(&s, op2 + op1);
                    break;
                case '-':
                    push(&s, op2 - op1);
                    break;
                case '*':
                    push(&s, op2 * op1);
                    break;
                case '/':
                    push(&s, op2 / op1);
                    break;
                default:
                    printf("Invalid operator\n");
                    exit(1);
            }
        }
    }

    return pop(&s);
}

int main() {
    char expr[] = "23+45+*";
    int result = evaluate_postfix(expr);
    printf("Result: %d\n", result);
    return 0;
}