C++ 代码

#include<iostream>
#include<algorithm>
#include<cstring>
#include<cstdio>
#include<string>
#include<queue>
#define INF 0x3f3f3f3f
using namespace std;
const int maxn = 1e5 + 5;
int head[maxn],Next[maxn],ver[maxn],edge[maxn];
int dist[maxn],vis[maxn];
int n,m,tot;
int main(void) {
    void add(int x,int y,int w);
    void spfa();
    memset(dist,0x3f,sizeof(dist));
    memset(vis,0,sizeof(vis));
    scanf("%d%d",&n,&m);
    int x,y;
    for(int i = 1; i <= m; i ++) {
        scanf("%d%d",&x,&y);
        add(x,y,1);
    }
    spfa();
    if(dist[n] == INF) cout<<-1<<endl;
    else cout<<dist[n]<<endl;
    return 0;
}
void add(int x,int y,int w) {
    ver[++tot] = y,edge[tot] = w;
    Next[tot] = head[x],head[x] = tot;
    return ;
}
void spfa() {
    queue<int>q;
    dist[1] = 0;
    q.push(1),vis[1] = 1;
    while(!q.empty()) {
        int x = q.front();
        q.pop();
        vis[x] = 0;
        for(int i = head[x]; i ; i = Next[i]) {
            int y = ver[i],z = edge[i];
            if(dist[y] > dist[x] + z) {
                dist[y] = dist[x] + z;
                if(vis[y] == 0) {
                    q.push(y);
                    vis[y] = 1;
                }
            }
        }
     }
     return;
}