847图中点的途径
作者:
一吱小晨
,
2022-10-19 01:16:20
,
所有人可见
,
阅读 168
#include<iostream>
#include<algorithm>
#include<cstring>
using namespace std;
const int N = 100010;
int n, m;
int h[N], e[N], ne[N], idx;
int d[N], q[N];
void add(int a, int b){
e[idx] = b;
ne[idx] = h[a];
h[a] = idx ++;
}
int bsf(){
int hh = 0, tt = 0;
q[0] = 1;
memset(d, -1, sizeof d);
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 (d[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 << bsf() <<endl;
return 0;
}