题解 | 小红的不动点分配

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

int main() {
    int n, a, maxCount = 0;
    scanf("%d", &n);
    int* cnt = (int*)calloc(n + 1, sizeof(int));
    for (int i = 0; i < 2 * n; ++i) {
        scanf("%d", &a);
        if (a <= n) {
            ++cnt[a];
        }
    }
    for (int i = 1; i <= n; ++i) {
        maxCount += cnt[i] > 2 ? 2 : cnt[i];
    }
    printf("%d\n", maxCount);
    free(cnt);
    return 0;
}