Overlooking the captivating blend of myriads of vernal hues, Arkady the painter lays out a long, long canvas.
Arkady has a sufficiently large amount of paint of three colours: cyan, magenta, and yellow. On the one-dimensional canvas split into n consecutive segments, each segment needs to be painted in one of the colours.
Arkady has already painted some (possibly none or all) segments and passes the paintbrush to you. You are to determine whether there are at least two ways of colouring all the unpainted segments so that no two adjacent segments are of the same colour. Two ways are considered different if and only if a segment is painted in different colours in them.
Input
The first line contains a single positive integer n (1 ≤ n ≤ 100) — the length of the canvas.
The second line contains a string s of n characters, the i-th of which is either ‘C’ (denoting a segment painted in cyan), ‘M’ (denoting one painted in magenta), ‘Y’ (one painted in yellow), or ‘?’ (an unpainted one).
Output
If there are at least two different ways of painting, output "Yes"; otherwise output "No" (both without quotes).
You can print each character in any case (upper or lower).
Examples
Input
5
CY??Y
Output
Yes
Input
5
C?C?Y
Output
Yes
Input
5
?CYC?
Output
Yes
Input
5
C??MM
Output
No
Input
3
MMY
Output
No
代码
#include<bits/stdc++.h>
using namespace std;
string s;
int main()
{
int n;
cin>>n;
getchar();
cin>>s;
int sum=0,flag=0,flag1=0,flag2=1;
for(int i=0;i<s.size();i++)
{
if(s[i]==s[i+1]&&s[i]!='?'&&s[i+1]!='?')
{
flag2=0;
break;//如果已经输入的连续的俩个数 相等并且不是问号不成立（首先判断）
}
else
{
if(s[i]=='?')
{
sum++;//判断有几个问号
if(s[i-1]=='?'||s[i+1]=='?')
flag=1;//如果有俩个连续问号则成立
else
if(s[i-1]==s[i+1])
flag1=1;//如果问号俩边的数相等则成立
}
}
}
if(n==1&&s[0]=='?')
{
puts("Yes");//如果只有一个数并且这个数是问号的话成立
return 0;
}
if(!flag2||sum==0||n==1)//如果本身错误或者没有问号或者只有一个数的话不成立
puts("No");
else
{
if(sum==1)//如果有一个问号
{
if(s[0]=='?'||s[s.size()-1]=='?')
puts("Yes");//如果问号在开头或者末尾成立
else
{
if(!flag1)//如果问号左右俩边不相等
puts("No");
else//如果问号左右俩边相等
puts("Yes");
}
}
else//否则有多个问号
{
if(flag)// 如果俩个问号挨着
{
puts("Yes");
}
else if(s[0]=='?'||s[s.size()-1]=='?')//如果有一个问号在开头或者末尾
puts("Yes");
else
{
if(!flag1) //如果每个问号左右俩边的数不相等
puts("No");
else //如果有一个问号的左右 相等
puts("Yes");
}
}
} return 0;
}