数据结构栈和队列表达式求值c语言

栈和队列是数据结构中常用的两种数据结构，它们可以被用来实现表达式求值。下面是一个使用栈和队列实现表达式求值的C语言例子：

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

#define MAX_STACK_SIZE 100
#define MAX_QUEUE_SIZE 100

typedef enum {
    lparen, rparen, plus, minus, times, divide, mod, eos, operand
} precedence;

int isp[] = { 0, 19, 12, 12, 13, 13, 13, 0 };
int icp[] = { 20, 19, 12, 12, 13, 13, 13, 0 };

precedence getToken(char *symbol, int *n) {
    *symbol = expr[(*n)++];
    switch (*symbol) {
        case '(': return lparen;
        case ')': return rparen;
        case '+': return plus;
        case '-': return minus;
        case '*': return times;
        case '/': return divide;
        case '%': return mod;
        case '\0': return eos;
        default: return operand;
    }
}

void postfix(void) {
    char symbol;
    precedence token;
    int n = 0;
    int top = 0;
    int queue_front = 0, queue_rear = 0;
    int stack[MAX_STACK_SIZE];
    char queue[MAX_QUEUE_SIZE][MAX_STACK_SIZE];

    stack[0] = eos;
    while ((token = getToken(&symbol, &n)) != eos) {
        if (token == operand) {
            queue[queue_rear][0] = symbol;
            queue[queue_rear++][1] = '\0';
        } else if (token == rparen) {
            while (stack[top] != lparen) {
                queue[queue_rear][0] = stack[top--];
                queue[queue_rear++][1] = '\0';
            }
            top--;
        } else {
            while (isp[stack[top]] >= icp[token]) {
                queue[queue_rear][0] = stack[top--];
                queue[queue_rear++][1] = '\0';
            }
            stack[++top] = token;
        }
    }
    while ((token = stack[top--]) != eos) {
        queue[queue_rear][0] = token;
        queue[queue_rear++][1] = '\0';
    }
    printf("Postfix expression: ");
    for (int i = queue_front; i < queue_rear; i++) {
        printf("%s", queue[i]);
    }
    printf("\n");
}

int main() {
    char expr[MAX_STACK_SIZE];
    printf("Enter an infix expression: ");
    scanf("%s", expr);
    postfix(expr);
    return 0;
}