AcWing 847. 图中点的层次
原题链接
简单
作者:
梦都会空
,
2021-12-06 18:07:45
,
所有人可见
,
阅读 106
#include <iostream>
#include <cstring>
#include <algorithm>
using namespace std;
const int N = 100010;
int d[N];//到1的距离
int n,m;
int h[N], e[N], ne[N], idx;
int q[N];
void add(int a, int b)
{
e[idx] = b, ne[idx] = h[a], h[a] = idx ++ ;
}
int dfs()
{
int hp=0;
int tl=0;
q[0]=1;
memset(d, -1, sizeof d);
d[1]=0;
while(hp<=tl)
{
int t=q[hp++];
for (int i = h[t]; i != -1; i = ne[i])
{
int j = e[i];
if (d[j] == -1)
{
d[j] = d[t] + 1;
q[++tl]=j;
}
}
}
return d[n];
}
int main()
{
scanf("%d%d", &n, &m);
memset(h, -1, sizeof h);
for (int i = 0; i < m; i ++ )
{
int a, b;
scanf("%d%d", &a, &b);
add(a, b);
}
cout << dfs() << endl;
return 0;
}