poj 1719 Shooting Contest (二分匹配)

Shooting Contest

Time Limit: 1000MS		Memory Limit: 10000K
Total Submissions: 3812		Accepted: 1389		Special Judge

Description

Welcome to the Annual Byteland Shooting Contest. Each competitor will shoot to a target which is a rectangular grid. The target consists of r*c squares located in r rows and c columns. The squares are coloured white or black. There are exactly two white squares and r-2 black squares in each column. Rows are consecutively labelled 1,..,r from top to bottom and columns are labelled 1,..,c from left to right. The shooter has c shots. 

A volley of c shots is correct if exactly one white square is hit in each column and there is no row without white square being hit. Help the shooter to find a correct volley of hits if such a volley exists. 
Example 
Consider the following target: 

Volley of hits at white squares in rows 2, 3, 1, 4 in consecutive columns 1, 2, 3, 4 is correct. 
Write a program that: verifies whether any correct volley of hits exists and if so, finds one of them.

Input

The first line of the input contains the number of data blocks x, 1 <= x <= 5. The following lines constitute x blocks. The first block starts in the second line of the input file; each next block starts directly after the previous one. 

The first line of each block contains two integers r and c separated by a single space, 2 <= r <= c <= 1000. These are the numbers of rows and columns, respectively. Each of the next c lines in the block contains two integers separated by a single space. The integers in the input line i + 1 in the block, 1 <= i <= c, are labels of rows with white squares in the i-th column. 

Output

For the i-th block, 1 <= i <= x, your program should write to the i-th line of the standard output either a sequence of c row labels (separated by single spaces) forming a correct volley of hits at white squares in consecutive columns 1, 2, ..., c, or one word NO if such a volley does not exists.

Sample Input

2
4 4
2 4
3 4
1 3
1 4
5 5
1 5
2 4
3 4
2 4
2 3

Sample Output

2 3 1 4
NO

Source

CEOI 1997

 

    开始没弄清楚题意，WA了两次，题意是给出一个n*m的矩形，每一列有两格是白色的，要求匹配出每列一个，每行至少一个的匹配。不行输出NO。

    先正常进行最大匹配，输出结果时把没匹配到的列随便分配两个中的一个即可。

//220K    110MS    C++    1341B    2014-06-03 15:44:38
//每列一个，每行至少一个 
#include<iostream>
#include<vector>
#define N 1005
using namespace std;
vector<int>V[N];
int vis[N];
int match[N];
int p[N][2];
int n,m;
int dfs(int u)
{
    for(int i=0;i<V[u].size();i++){
        int v=V[u][i];
        if(!vis[v]){
            vis[v]=1;
            if(match[v]==-1 || dfs(match[v])){
                match[v]=u;
                return 1;
            }
        }
    }
    return 0;
}
int hungary()
{
    memset(match,-1,sizeof(match));
    int ret=0;
    for(int i=1;i<=m;i++){
        memset(vis,0,sizeof(vis));
        ret+=dfs(i);
    }
    return ret;
}
int main(void)
{
    int t;
    scanf("%d",&t);
    while(t--)
    {
        scanf("%d%d",&n,&m);
        for(int i=0;i<=m;i++) V[i].clear();
        for(int i=1;i<=m;i++){
            scanf("%d%d",&p[i][0],&p[i][1]);
            V[i].push_back(p[i][0]);
            V[i].push_back(p[i][1]);
        }
        int prt[N]={0};
        if(hungary()==n){
            for(int i=1;i<=n;i++)
                prt[match[i]]=i;
            for(int i=1;i<m;i++)
                if(prt[i]==0) printf("%d ",p[i][0]);
                else printf("%d ",prt[i]);
            if(prt[m]==0) printf("%d
",p[m][0]); 
            else printf("%d
",prt[m]);
        }else puts("NO");
    }
    return 0;
}