http://poj.org/problem?id=1719

Shooting Contest
Time Limit: 1000MS   Memory Limit: 10000K
Total Submissions: 4135   Accepted: 1521   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 题意比较难理解,题意弄懂后这道题就比较简单,套用匈牙利算法求最大匹配 题目大意:r*c的矩阵,矩阵由白格子和黑格子组成,每一列有两个格子是白色的剩下的为黑色,每一列射击一发子弹击中白色格子,问是否所有行都有白色格子被击中 数据分析:
2//数据组数
4 4//行r 列c
2 4//第1列的第2行和第4行是白色格子
3 4//第2列的第3行和第4行是白色格子
1 3//第3列的第1行和第3行是白色格子
1 4// ...
1.如果 r > c , c列射击完后仍会有行没有被射击过;
2.要从每一列开始射击并射中白色格子,即将行r和列c作为X,Y集合,白色格子部分进行匹配,得到最大匹配值ans
1>如果ans==r
(1)如果每一列都有匹配(即都能射中某一行的白色格子)就输出与该列匹配的行(即该列击中的的白色格子所在的行)
(2)如果某一列没有找到匹配的格子,那个只要在该行任意选择一个白色的格子就可以了,输出该白色格子所在的行
2>如果ans>r或者ans<r都无法满足每行都被射击过
#include<stdio.h>
#include<string.h>
#include<math.h>
#include<stdlib.h>
#include<queue>
#include<algorithm>
#define INF 0x3f3f3f3f
#define N 1010 using namespace std; int G[N][N], vis[N], used[N];
int r, c; bool Find(int u)
{
int i;
for(i = ; i <= c ; i++)
{
if(!vis[i] && G[u][i])
{
vis[i] = ;
if(!used[i] || Find(used[i]))
{
used[i] = u;
return true;
}
}
}
return false;
}//匈牙利 int main()
{
int a, b, i, t;
scanf("%d", &t);
while(t--)
{
scanf("%d%d", &r, &c);
if(r > c)
{
printf("NO\n");
continue;
}//如果 r > c , c列射击完后仍会有行没有被射击过
memset(G, , sizeof(G));
for(i = ; i <= c ; i++)
{
scanf("%d%d", &a, &b);
G[a][i] = G[b][i] = ;//第i列个第a行和第b行是白色格子
}
memset(used, , sizeof(used));
int ans = ;
for(i = ; i <= r ; i++)
{
memset(vis, , sizeof(vis));
if(Find(i))
ans++;
}
if(ans == r)
{
for(i = ; i <= c ; i++)
{
if(used[i] != )//如果每一列都有匹配(即都能射中某一行的白色格子)就输出与该列匹配的行(即该列击中的的白色格子所在的行)
printf("%d ", used[i]);
else
{
for(int j = ; j <= r ; j++)
{
if(G[j][i])
{
printf("%d ", j);
break;
}
}
}//如果某一列没有找到匹配的格子,那个只要在该行任意选择一个白色的格子就可以了,输出该白色格子所在的行;
}
printf("\n");
}
else//如果ans>r或者ans<r都无法满足每行都被射击过
printf("NO\n");
}
return ;
}


 
												

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