C语言：算数表达式求值，输入9+3*6，输出27

以下是一个基本的C语言算术表达式求值程序，可以实现你想要的功能：

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

#define MAX_EXPR_LEN 100

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

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

void push(Stack *s, int val) {
    s->data[++s->top] = val;
}

int pop(Stack *s) {
    return s->data[s->top--];
}

int peek(Stack *s) {
    return s->data[s->top];
}

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

int evaluate(char *expr) {
    Stack operands;
    Stack operators;
    int i, op1, op2, result;

    init(&operands);
    init(&operators);

    for (i = 0; expr[i] != '\0'; i++) {
        if (isdigit(expr[i])) {
            push(&operands, expr[i] - '0');
        } else if (expr[i] == '+' || expr[i] == '-' || expr[i] == '*' || expr[i] == '/') {
            while (!is_empty(&operators) && peek(&operators) != '(' && ((expr[i] == '*' || expr[i] == '/') || (expr[i] == '+' || expr[i] == '-') && (peek(&operators) == '*' || peek(&operators) == '/'))) {
                op2 = pop(&operands);
                op1 = pop(&operands);

                switch (pop(&operators)) {
                    case '+':
                        result = op1 + op2;
                        break;
                    case '-':
                        result = op1 - op2;
                        break;
                    case '*':
                        result = op1 * op2;
                        break;
                    case '/':
                        result = op1 / op2;
                        break;
                }

                push(&operands, result);
            }

            push(&operators, expr[i]);
        } else if (expr[i] == '(') {
            push(&operators, expr[i]);
        } else if (expr[i] == ')') {
            while (peek(&operators) != '(') {
                op2 = pop(&operands);
                op1 = pop(&operands);

                switch (pop(&operators)) {
                    case '+':
                        result = op1 + op2;
                        break;
                    case '-':
                        result = op1 - op2;
                        break;
                    case '*':
                        result = op1 * op2;
                        break;
                    case '/':
                        result = op1 / op2;
                        break;
                }

                push(&operands, result);
            }

            pop(&operators);
        }
    }

    while (!is_empty(&operators)) {
        op2 = pop(&operands);
        op1 = pop(&operands);

        switch (pop(&operators)) {
            case '+':
                result = op1 + op2;
                break;
            case '-':
                result = op1 - op2;
                break;
            case '*':
                result = op1 * op2;
                break;
            case '/':
                result = op1 / op2;
                break;
        }

        push(&operands, result);
    }

    return pop(&operands);
}

int main() {
    char expr[MAX_EXPR_LEN];

    printf("Enter an arithmetic expression: ");
    scanf("%s", expr);

    printf("Result: %d\n", evaluate(expr));

    return 0;
}

你可以输入9+3*6，程序会输出27。