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//
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// Created by Rock Zhang on 2025/9/23.
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//
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#include <stdio.h>
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#include <string.h>
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#include <stdlib.h>
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#include <ctype.h>
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#define MAX 100
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typedef struct
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{
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    int data[MAX];
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    int top;
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}Stack;
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void initStack(Stack* stack)
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{
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    stack -> top = -1;
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}
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void push(Stack* stack, int data)
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{
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    stack -> data[++stack -> top] = data;
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}
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int pop(Stack* stack)
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{
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    return stack -> data[stack -> top--];
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}
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int calc()
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{
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    Stack stack;
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    initStack(&stack);
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    char token[MAX];
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    while (1)
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    {
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        scanf("%s", token);
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        if (strcmp(token, "=") == 0)
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        {
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            break;
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        }
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        int is_number = 1;
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        for (int i = 0; token[i] != '\0'; i++) {
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            if (!isdigit(token[i])) {
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                is_number = 0;
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                break;
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            }
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        }
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        if (is_number) {
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            int number = atoi(token);
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            push(&stack, number);
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            printf("-> 输入数字: %d\n", number);
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        }
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        else if (strlen(token) == 1)
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        {
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            char operator = token[0];
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            int a = 0, b = 0, result = 0;
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            b = pop(&stack);
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            a = pop(&stack);
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            switch (operator)
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            {
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                case '+':
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                    printf("输入算符 +\n");
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                    result = a + b;
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                    break;
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                case '-':
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                    result = a - b;
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                    break;
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                case '*':
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                    result = a * b;
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                    break;
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                case '/':
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                    result = a / b;
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                    break;
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                default:
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                    printf("错误: 未知运算符 '%c'。\n", operator);
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            }
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            push(&stack, result);
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        }
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    }
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    printf("%d", pop(&stack));
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    return 0;
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}
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int main()
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{
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    calc();
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    return 0;
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}