567-Risk // bfs

Because there is no weight value, you do not need to use the Floyd algorithm to find the shortest path.

Directly use bfs...

#include<cstdio>#include<cstring>using namespace std;const int maxn = 21;int G[maxn][maxn];int vis[maxn][maxn];struct node{    int level;    int u;} q[maxn*maxn];int bfs(int s,int e){    int front = 1;    int rear = 1;    q[1].u = s;    q[1].level = 0;    while(front <= rear)    {        int u = q[front].u;        int level = q[front++].level;        if(u == e) return level;        for(int v = 1; v <= 20; v++)        {            if(G[u][v] && !vis[u][v])            {                vis[u][v] = vis[v][u] = 1;                q[++rear].level = level + 1;                q[rear].u = v;            }        }    }}int main(){    int begin,T = 0;    while(scanf("%d",&begin) != EOF)    {        T++;        memset(G,0,sizeof(G));        int a,num,t;        for(int i = 0; i < begin; i++)        {            scanf("%d",&a);            G[1][a] = G[a][1] = 1;        }        for(int i = 1; i < 19; i++)        {            scanf("%d",&num);            for(int j = 0; j < num; j++)            {                scanf("%d",&a);                G[i+1][a] = G[a][i+1] = 1;            }        }        printf("Test Set #%d\n",T);        scanf("%d",&t);        int s,e;        for(int i = 0; i < t; i++)        {            memset(vis,0,sizeof(vis));            scanf("%d%d",&s,&e);            printf("%2d to %2d: %d\n",s,e,bfs(s,e));        }        printf("\n");    }    return 0;}