AcWing 847. 图中点的层次
原题链接
简单
作者:
qgc123
,
2021-11-30 14:38:04
,
所有人可见
,
阅读 160
#include<bits/stdc++.h>
using namespace std;
const int N = 1e6 + 10;
int e[N], ne[N], h[N], idx, n, m, q[N], d[N], st[N];
void add(int a, int b){
e[idx] = b, ne[idx] = h[a], h[a] = idx++;
}
int bfs(){
int hh = 0, tt = 0;
memset(d, -1, sizeof d);
q[0] = 1;
d[1] = 0;
while(hh <= tt){
int t = q[hh++];
for(int i = h[t]; i != -1; i = ne[i]){
int j = e[i];
if(!st[j]){
st[j] = 1;
d[j] = d[t] + 1;
q[++tt] = j;
}
}
}
return d[n];
}
int main(){
cin >> n >> m;
memset(h, -1, sizeof h);
for(int i = 0; i < m; i++){
int a, b;
cin >> a >> b;
add(a, b);
}
cout << bfs() << endl;
}