题解 (C语言)

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

#define MAXN 100001

int max(int a, int b) {
    return a > b ? a : b;
}

int main() {
    int n;
    scanf("%d", &n);
    int arr[n];
    for (int i = 0; i < n; i++) {
        scanf("%d", &arr[i]);
    }
    for (int i = 0; i < n; i++) {
        if (arr[i] > 0) {
            arr[i] = 1;
        } else if (arr[i] < 0) {
            arr[i] = -1;
        }
    }
    int* prefixSumIndex = (int*)malloc((2 * n + 1) * sizeof(int));
    memset(prefixSumIndex, -1, (2 * n + 1) * sizeof(int));
    int sum = n;
    int maxLength = 0;
    prefixSumIndex[sum] = 0; 
    for (int i = 0; i < n; i++) {
        sum += arr[i];
        if (prefixSumIndex[sum] != -1) {
            maxLength = max(maxLength, i - prefixSumIndex[sum] + 1);
        } else {
            prefixSumIndex[sum] = i + 1; 
        }
    }
    printf("%d\n", maxLength);
    free(prefixSumIndex);
    return 0;
}