c语言用栈实现计算器（中缀表达式）

栈是实现计算器的核心数据结构，可以用来存储运算符和操作数。下面是使用栈实现中缀表达式计算器的C语言代码：

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

#define MAX_SIZE 50

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

void push(Stack *s, int value) {
    if (s->top == MAX_SIZE - 1) {
        printf("Stack Overflow\n");
        return;
    }

    s->data[++(s->top)] = value;
}

int pop(Stack *s) {
    if (s->top == -1) {
        printf("Stack Underflow\n");
        exit(1);
    }

    return s->data[(s->top)--];
}

bool is_operator(char ch) {
    return ch == '+' || ch == '-' || ch == '*' || ch == '/';
}

int get_priority(char op) {
    switch (op) {
        case '(':
            return 0;
        case '+':
        case '-':
            return 1;
        case '*':
        case '/':
            return 2;
        default:
            return -1;
    }
}

int calculate(int op1, int op2, char operator) {
    switch (operator) {
        case '+':
            return op1 + op2;
        case '-':
            return op1 - op2;
        case '*':
            return op1 * op2;
        case '/':
            return op1 / op2;
        default:
            return -1;
    }
}

int evaluate_expression(char *expression) {
    Stack operand_stack;
    Stack operator_stack;
    operand_stack.top = -1;
    operator_stack.top = -1;
    int i = 0;

    while (expression[i] != '\0') {
        if (isdigit(expression[i])) {
            int operand = 0;
            while (isdigit(expression[i])) {
                operand = operand * 10 + (expression[i] - '0');
                i++;
            }
            push(&operand_stack, operand);
        } else if (is_operator(expression[i])) {
            while (operator_stack.top >= 0 && get_priority(expression[i]) <= get_priority(operator_stack.data[operator_stack.top])) {
                int op2 = pop(&operand_stack);
                int op1 = pop(&operand_stack);
                char op = pop(&operator_stack);
                int result = calculate(op1, op2, op);
                push(&operand_stack, result);
            }
            push(&operator_stack, expression[i]);
            i++;
        } else if (expression[i] == '(') {
            push(&operator_stack, expression[i]);
            i++;
        } else if (expression[i] == ')') {
            while (operator_stack.data[operator_stack.top] != '(') {
                int op2 = pop(&operand_stack);
                int op1 = pop(&operand_stack);
                char op = pop(&operator_stack);
                int result = calculate(op1, op2, op);
                push(&operand_stack, result);
            }
            pop(&operator_stack);
            i++;
        } else {
            i++;
        }
    }

    while (operator_stack.top >= 0) {
        int op2 = pop(&operand_stack);
        int op1 = pop(&operand_stack);
        char op = pop(&operator_stack);
        int result = calculate(op1, op2, op);
        push(&operand_stack, result);
    }

    return pop(&operand_stack);
}

int main() {
    char str[MAX_SIZE];
    printf("Enter expression: ");
    scanf("%s", str);
    int result = evaluate_expression(str);
    printf("Result: %d\n", result);
    return 0;
}

这个程序支持加、减、乘、除和括号，可以计算包括负数在内的表达式。你可以在控制台中输入一个表达式，程序会输出计算结果。