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2 years ago
#include <bits/stdc++.h>
using namespace std;
int n, m;
/*
4 3
1 2
1 3
1 4
0
1
2
3
*/
const int N = 110;
struct Node {
int l, r, f;
} tr[N];
int root[N], rs;
bool a[N][N];
int main() {
//文件输入
freopen("DuoChaShuToErChaShu.in", "r", stdin);
scanf("%d %d", &n, &m);
for (int i = 1; i <= m; i++) { // m条边
int x, y;
scanf("%d %d", &x, &y);
a[x][y] = true; // x->y有一条边先保存起来
}
for (int i = 1; i <= n; i++) //双层循环,枚举每个点到点的关系
for (int j = 1; j <= n; j++)
if (a[i][j]) { //如果i->j有一条边
if (tr[i].l == 0) { // i没有左儿子
tr[i].l = j; // j就是i的左儿子
tr[j].f = i; // i是j的父亲
} else {
int t = tr[i].l; //找到i的左儿子
while (tr[t].r) t = tr[t].r; //一路向下找i的右儿子右儿子,右儿子...
tr[t].r = j; // j做为最终的右儿子
tr[j].f = t; // j的父亲是最终的右儿子
}
}
//处理森林
for (int i = 1; i <= n; i++)
if (!tr[i].f) root[++rs] = i; //将每个子树的根加入到root数组
for (int i = rs; i > 1; i--) { //保留一个根,其它的根合并到前一个根中,从右向左当做右儿子加入
tr[root[i - 1]].r = root[i];
tr[root[i]].f = root[i - 1];
}
//输出每个点的父节点号
for (int i = 1; i <= n; i++) printf("%d\n", tr[i].f);
return 0;
}