题解 | #四则运算#

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

int i = 0;
int  calculate(char* a)
{
    int len = strlen(a);
    int stack[100] = { 0 };
    int i_stack = 0;

    int flag = '+';
    while (i < len)
    {
        int n = 0;
        if (a[i] == '(' || a[i] == '[' || a[i] == '{')
        {
            i++;
            n = calculate(a);
        }

        while (isdigit(a[i]) && i < len)
        {
            n = n * 10 + a[i++] - '0';
        }
        switch (flag)
        {
        case '+':
            stack[i_stack++] = n;
            break;
        case '-':
            stack[i_stack++] = -n;
            break;
        case '*':
            stack[i_stack - 1] *= n;
            break;
        case '/':
            stack[i_stack - 1] /= n;
            break;
        }

        if (a[i] == ')' || a[i] == ']' || a[i] == '}') {
            i++;
            break;
        }
        flag = a[i++];
    }
    int sum = 0;
    for (int j = 0; j < i + 1; j++)
        sum += stack[j];
    return sum;
}

int main()
{
    char arr[100] = { 0 };
    scanf("%s", &arr);
    int i = 0;
    int n = calculate(arr);
    printf("%d\n", n);
    return 0;
}