hdu 5385 The path 2015多校联合训练赛#8 bfs

The path

Time Limit: 4000/2000 MS (Java/Others)    Memory Limit: 65536/65536 K (Java/Others)
Total Submission(s): 282    Accepted Submission(s): 76
Special Judge

Problem Description

You have a connected directed graph.Let  d(x)  be the length of the shortest path from  1  to  x .Specially  d(1)=0 .A graph is good if there exist  x  satisfy  d(1)<d(2)<....d(x)>d(x+1)>...d(n) .Now you need to set the length of every edge satisfy that the graph is good.Specially,if  d(1)<d(2)<..d(n) ,the graph is good too.

The length of one edge must  ∈   [1,n]

It's guaranteed that there exists solution.

 

Input

There are multiple test cases. The first line of input contains an integer  T , indicating the number of test cases. For each test case:
The first line contains two integers n and m,the number of vertexs and the number of edges.Next m lines contain two integers each,  ui  and  vi   (1≤ui,vi≤n) , indicating there is a link between nodes  ui  and  vi  and the direction is from  ui  to  vi .

∑n≤3∗105 , ∑m≤6∗105
1≤n,m≤105

 

Output

For each test case,print  m  lines.The i-th line includes one integer:the length of edge from  ui  to  vi

 

Sample Input

   
   
   
   

    
    
    
    2
4 6
1 2
2 4
1 3
1 2
2 2
2 3
4 6
1 2
2 3
1 4
2 1
2 1
2 1
   
   
   
   

 

Sample Output

   
   
   
   

    
    
    
    1
2
2
1
4
4
1
1
3
4
4
4
   
   
   
   

 

Source

2015 Multi-University Training Contest 8

每个点距离1-n，知道距离后，U-v的边就是abs(dist[u]-dist[v])

所以从1，n两个方向开始bfs

#include<iostream>
#include<cstring>
#include<algorithm>
#include<cstdio>
#include<set>
using namespace std;
#define maxn 100007

int head[maxn];
int cnt;
struct Edge{
    int v,u,next;
};
int dist[maxn];
Edge edge[maxn];
void addedge(int u,int v){
    edge[cnt].v = v;
    edge[cnt].u = u;
    edge[cnt].next = head[u];
    head[u] = cnt++;
}
int check[maxn];
int main(){
    int t,n,m;
    scanf("%d",&t);
    while(t--){
        scanf("%d%d",&n,&m);
        cnt = 0;
        for(int i = 0;i <= n; i++){
            check[i] = 0;
            head[i] = -1;
        }
        int u,v;
        for(int i = 0;i < m; i++){
            scanf("%d%d",&u,&v);
            addedge(u,v);
        }
        check[1] = 1;
        check[n] = 1;
        int l = 1, r = n;
        for(int i = 1;i <= n; i++){
            if(check[l] == 0)
                u = r--;
            else u = l++;
            dist[u] = i;
            for(int j = head[u]; j != -1; j=edge[j].next){
                v = edge[j].v;
                check[v] = 1;
            }
        }
        for(int i = 0;i < m; i++){
            u = edge[i].u;
            v = edge[i].v;
            if(dist[u] < dist[v])
                printf("%d\n",dist[v]-dist[u]);
            else printf("%d\n",n);
        }

    }
    return 0;
}

/*
22
4 3
1 2
1 4
4 3
4 6
1 2
2 4
1 3
1 2
2 2
2 3
4 6
1 2
2 3
1 4
2 1
2 1
2 1
*/