题解 | #挑选镇长#

#include <stdio.h>
#include <math.h>
void init(int arr[],int len){
    int k=0;
    for(k=0;k<len;k++){
        arr[k]=0;
    }
}

int main() {
    int t = 0, n = 0, m = 0;
    int i = 0, j = 0;
    int tmp1 = 0, tmp2 = 0;
    int num = 0;
    int app[1000] = { 0 };
    scanf("%d", &t);
    int in[100000] = { 0 };
    int out[100000] = { 0 };
    for (i = 0; i < t; i++) {
        scanf("%d %d", &n, &m);
        for (j = 0; j < m; j++) {
            scanf("%d %d", &tmp1, &tmp2);
            if (tmp1 != tmp2) {
                out[tmp1 - 1]++;
                in[tmp2 - 1]++;
            }

        }
        for (j = 0; j < n; j++) {
            if (in[j] == n - 1 && out[j] == 0) {
                app[num] = j+1;
                num++;
            }
        }
        if (num == 0) {
            printf("0\n");
            printf("\n");
        }
        else {
            printf("%d\n", num);
            for (j = 0; j < num; j++) {
                printf("%d ", app[j]);
            }
            printf("\n");
        }
        num=0;
        init(app,1000);
        init(in,100000);
        init(out,100000);
    }
    return 0;
}