N - Tram——最短路_spfa()算法

Think:
1知识点：最短路_spfa()算法
2思考：理解题意进而建图

vjudge题目链接

以下为Accepted代码

#include 
#include 
#include 
#include 

using namespace std;

const int inf = 0x3f3f3f3f;
const int N = 1e2 + 4;

int n, e[N][N], vis[N], dis[N];

void spfa(int x);

int main(){
    int x, y, k, i, j, v;
    while(~scanf("%d %d %d", &n, &x, &y)){
        memset(e, inf, sizeof(e));
        for(i = 1; i <= n; i++){
            scanf("%d", &k);
            for(j = 0; j < k; j++){
                scanf("%d", &v);
                if(!j)
                    e[i][v] = 0;
                else
                    e[i][v] = 1;
            }
        }
        spfa(x);
        if(dis[y] != inf)
            printf("%d\n", dis[y]);
        else
            printf("-1\n");
    }
    return 0;
}
void spfa(int x){
    queue <int> q;
    while(!q.empty()){
        q.pop();
    }
    memset(dis, inf, sizeof(dis));
    memset(vis, 0, sizeof(vis));
    dis[x] = 0, vis[x] = 1;
    q.push(x);
    while(!q.empty()){
        int t1 = q.front();
        q.pop();
        vis[t1] = 0;
        for(int i = 1; i <= n; i++){
            if(dis[t1] + e[t1][i] < dis[i]){
                dis[i] = dis[t1] + e[t1][i];
                if(!vis[i]){
                    vis[i] = 1;
                    q.push(i);
                }
            }
        }
    }
}