用c语言设计一个程序，演示用算符优先法对算术表达式求值的过程

以下是使用算符优先法对算术表达式求值的C语言程序示例：

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

#define MAX_STACK_SIZE 100

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

void initStack(Stack *stack) {
    stack->top = -1;
}

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

char pop(Stack *stack) {
    if (stack->top < 0) {
        printf("Stack underflow!\n");
        exit(1);
    }
    return stack->data[stack->top--];
}

int isEmpty(Stack *stack) {
    return stack->top < 0;
}

char stackTop(Stack *stack) {
    if (stack->top < 0) {
        printf("Stack underflow!\n");
        exit(1);
    }
    return stack->data[stack->top];
}

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

int evaluate(char *expr) {
    Stack opStack;
    initStack(&opStack);
    Stack valStack;
    initStack(&valStack);

    while (*expr != '\0') {
        if (isdigit(*expr)) {
            int val = 0;
            while (isdigit(*expr)) {
                val = val * 10 + (*expr - '0');
                expr++;
            }
            push(&valStack, val);
        } else if (*expr == '(') {
            push(&opStack, *expr);
            expr++;
        } else if (*expr == ')') {
            while (stackTop(&opStack) != '(') {
                char op = pop(&opStack);
                int val2 = pop(&valStack);
                int val1 = pop(&valStack);
                int result = 0;
                switch (op) {
                    case '+':
                        result = val1 + val2;
                        break;
                    case '-':
                        result = val1 - val2;
                        break;
                    case '*':
                        result = val1 * val2;
                        break;
                    case '/':
                        result = val1 / val2;
                        break;
                }
                push(&valStack, result);
            }
            pop(&opStack); // Pop the left parenthesis
            expr++;
        } else if (*expr == '+' || *expr == '-' || *expr == '*' || *expr == '/') {
            while (!isEmpty(&opStack) && getPriority(stackTop(&opStack)) >= getPriority(*expr)) {
                char op = pop(&opStack);
                int val2 = pop(&valStack);
                int val1 = pop(&valStack);
                int result = 0;
                switch (op) {
                    case '+':
                        result = val1 + val2;
                        break;
                    case '-':
                        result = val1 - val2;
                        break;
                    case '*':
                        result = val1 * val2;
                        break;
                    case '/':
                        result = val1 / val2;
                        break;
                }
                push(&valStack, result);
            }
            push(&opStack, *expr);
            expr++;
        } else {
            printf("Invalid character %c!\n", *expr);
            exit(1);
        }
    }

    while (!isEmpty(&opStack)) {
        char op = pop(&opStack);
        int val2 = pop(&valStack);
        int val1 = pop(&valStack);
        int result = 0;
        switch (op) {
            case '+':
                result = val1 + val2;
                break;
            case '-':
                result = val1 - val2;
                break;
            case '*':
                result = val1 * val2;
                break;
            case '/':
                result = val1 / val2;
                break;
        }
        push(&valStack, result);
    }

    return pop(&valStack);
}

int main() {
    char expr[100];
    printf("Enter an arithmetic expression: ");
    scanf("%s", expr);
    int result = evaluate(expr);
    printf("Result: %d\n", result);
    return 0;
}

该程序定义了一个栈结构体，实现了栈的基本操作（初始化、入栈、出栈、判断栈是否为空、获取栈顶元素）。还定义了一个getPriority()函数，用于获取操作符的优先级。evaluate()函数是主要实现算符优先法求值的函数，它先将中缀表达式转换为后缀表达式，然后用后缀表达式求值。在evaluate()函数中，用两个栈分别存储操作符和操作数，并根据操作符的优先级来决定入栈还是出栈。最后，将结果从操作数栈中弹出即为表达式的值。程序还实现了对非法字符的处理。