View Code of Problem 3457

#include<iostream>
#include<cstring>
#include<cstdio>
#include<algorithm>
#include<queue>
using namespace std;

const int MAXN = 51;
int Graph[MAXN][MAXN],visit[MAXN];
int pre[MAXN];
int n,m,k;
 queue<int>myqueue;
int bfs()
{
    int h,i,dist[55];
    memset(dist,0,sizeof(dist));

    while (!myqueue.empty()) myqueue.pop();
    myqueue.push(1);
    dist[1]=0;
    while (!myqueue.empty())
    {
        h=myqueue.front();
        myqueue.pop();
        if (h==n) break;
        for (i=1; i<=n; i++)
            if (Graph[h][i] && !visit[i] && dist[i]==0)
            {
                dist[i]=dist[h]+1;
                pre[i]=h;
                myqueue.push(i);
            }
    }
    return dist[n];
}

int solve(int cnt)
{

    int dis = bfs();

    if(dis > k||dis == 0){
        return 1;
    }
    else if(cnt == 0){
        return 0;
    }
    else
    {
        int way[55];
        int j = pre[n];
        int t = dis;
        while(j!=1)
        {
            way[--t] = j;
            j = pre[j];
        }
        for(int i = 1; i < dis; i ++)
        {
            visit[way[i]] = 1;
            if(solve(cnt-1))return 1;
            visit[way[i]] = 0;
        }
    }
    return 0;
}

int main()
{
    int x,y,cnt;
    while(scanf("%d%d%d",&n,&m,&k),n+m+k)
    {
        memset(Graph,0,sizeof(Graph));
        memset(visit,0,sizeof(visit));
        for(int i = 0; i < m; i ++)
        {
            scanf("%d%d",&x,&y);
            Graph[x][y] =1;
        }
        int dis = bfs();
        if(dis > k||dis == 0){
            cnt = 0;
        }
        else{
            int way[55];
            int j = pre[n];
            int t = dis;
            while(j!=1){
                way[--t] = j;
                j = pre[j];
            }
            cnt = 0;
            int ok = 0;
            for(int i = 1; i <= n-1; i ++){
                memset(visit,0,sizeof(visit));
                for(int j = 1; j < dis; j ++){
                    visit[way[j]] = 1;
                    if(solve(i-1)){
                        cnt = i;
                        ok = 1;
                        break;
                    }
                    visit[way[j]] = 0;
                }
                if(ok)break;
            }
        }
        printf("%d\n",cnt);
    }
}