use MathJax to parse formulas
Description
Little Q loves playing with different kinds of graphs very much. One day he thought about an interesting category of graphs called ``Cool Graph'', which are generated in the following way:
Let the set of vertices be {1, 2, 3, ..., $n$}. You have to consider every vertice from left to right (i.e. from vertice 2 to $n$). At vertice $i$, you must make one of the following two decisions:
(1) Add edges between this vertex and all the previous vertices (i.e. from vertex 1 to $i-1$).
(2) Not add any edge between this vertex and any of the previous vertices.
In the mathematical discipline of graph theory, a matching in a graph is a set of edges without common vertices. A perfect matching is a matching that each vertice is covered by an edge in the set.
Now Little Q is interested in checking whether a ''Cool Graph'' has perfect matching. Please write a program to help him.
Let the set of vertices be {1, 2, 3, ..., $n$}. You have to consider every vertice from left to right (i.e. from vertice 2 to $n$). At vertice $i$, you must make one of the following two decisions:
(1) Add edges between this vertex and all the previous vertices (i.e. from vertex 1 to $i-1$).
(2) Not add any edge between this vertex and any of the previous vertices.
In the mathematical discipline of graph theory, a matching in a graph is a set of edges without common vertices. A perfect matching is a matching that each vertice is covered by an edge in the set.
Now Little Q is interested in checking whether a ''Cool Graph'' has perfect matching. Please write a program to help him.
Input
The first line of the input contains an integer $T(1\leq T\leq50)$, denoting the number of test cases.
In each test case, there is an integer $n(2\leq n\leq 100000)$ in the first line, denoting the number of vertices of the graph.
The following line contains $n-1$ integers $a_2,a_3,...,a_n(1\leq a_i\leq 2)$, denoting the decision on each vertice.
In each test case, there is an integer $n(2\leq n\leq 100000)$ in the first line, denoting the number of vertices of the graph.
The following line contains $n-1$ integers $a_2,a_3,...,a_n(1\leq a_i\leq 2)$, denoting the decision on each vertice.
Output
For each test case, output a string in the first line. If the graph has perfect matching, output ''Yes'', otherwise output ''No''.
Sample Input
3 2 1 2 2 4 1 1 2
Sample Output
Yes No No
题意：输入t组样例 每组样例先输入一个n 表示下面有n-1个数据 表示第2个到第n个点 每个数据只能是1或2 1代表可以和前面的任意一个点相连 2代表不可以和前面的相连 如果最终每两个点之间有且只有一条线 则输出yes 否则输出n：o
代码：
#include
<iostream>
#include <stdio.h>
#include <string.h>
#include <algorithm>
#include <string.h>
using namespace std ;
int a [ 100005 ];
int main ()
{
int t , n , b , ans ;
cin >> t ;
while ( t --)
{
memset ( a , 0 , sizeof ( a ));
#include <stdio.h>
#include <string.h>
#include <algorithm>
#include <string.h>
using namespace std ;
int a [ 100005 ];
int main ()
{
int t , n , b , ans ;
cin >> t ;
while ( t --)
{
memset ( a , 0 , sizeof ( a ));
cin
>>
n
;
for ( int i = 0 ; i < n -1 ; i ++)
scanf ( "%d" ,& a [ i ]);
ans = 1 ; //ans赋值为1表示此时没有相连的只有第一个
for ( int i = 0 ; i < n -1 ; i ++)
{
for ( int i = 0 ; i < n -1 ; i ++)
scanf ( "%d" ,& a [ i ]);
ans = 1 ; //ans赋值为1表示此时没有相连的只有第一个
for ( int i = 0 ; i < n -1 ; i ++)
{
if
(
ans
==
0
)
ans = 1 ; //新的这个没有连上
else
{
if ( a [ i ]== 1 )
ans --; //和前面的一个相连
else
ans ++; //如果a[i]是2 表示没有连上的又多了一个
}
}
if ( ans == 0 )
printf ( "Yes \n " );
else
printf ( "No \n " );
}
return 0 ;
}
ans = 1 ; //新的这个没有连上
else
{
if ( a [ i ]== 1 )
ans --; //和前面的一个相连
else
ans ++; //如果a[i]是2 表示没有连上的又多了一个
}
}
if ( ans == 0 )
printf ( "Yes \n " );
else
printf ( "No \n " );
}
return 0 ;
}