Alternative Thinking (interval intersection, greedy)

Kevin has just recevied his disappointing results on the USA Identification of Cows Olympiad (USAICO) in the form of a binary string of length n. Each character of Kevin’s string represents Kevin’s score on one of the n questions of the olympiad—‘1’ for a correctly identified cow and ‘0’ otherwise.

However, all is not lost. Kevin is a big proponent of alternative thinking and believes that his score, instead of being the sum of his points, should be the length of the longest alternating subsequence of his string. Here, we define an alternating subsequence of a string as a not-necessarily contiguous subsequence where no two consecutive elements are equal. For example, {0, 1, 0, 1}, {1, 0, 1}, and {1, 0, 1, 0} are alternating sequences, while {1, 0, 0} and {0, 1, 0, 1, 1} are not.

Kevin, being the sneaky little puffball that he is, is willing to hack into the USAICO databases to improve his score. In order to be subtle, he decides that he will flip exactly one substring—that is, take a contiguous non-empty substring of his score and change all '0’s in that substring to '1’s and vice versa. After such an operation, Kevin wants to know the length of the longest possible alternating subsequence that his string could have.
Input
The first line contains the number of questions on the olympiad n (1 ≤ n ≤ 100 000).

The following line contains a binary string of length n representing Kevin’s results on the USAICO.

Output
Output a single integer, the length of the longest possible alternating subsequence that Kevin can create in his string after flipping a single substring.

Examples
Input
8
10000011
Output
5
Input
2
01
Output
2
Note
In the first sample, Kevin can flip the bolded substring ‘10000011’ and turn his string into ‘10011011’, which has an alternating subsequence of length 5: ‘10011011’.

In the second sample, Kevin can flip the entire string and still have the same score.
Topic Analysis:
With this title may know that in fact a lot of questions about the transformation can be transformed into many basic questions, nothing more than to take on different details.
The question is no need to question it and just in time so accurate, if the temperature changes in the interval of the first person and second person of temperature change interval intersect or contain, the second person must be satisfied, and so on, replace every one person replacement at intervals around end, the left end point takes the maximum value, minimum value right point, because this is the most accurate, if the replacement is not added, then the left and right endpoints endpoint is infinite increase and decrease, the code to see details.

#include<iostream>
using namespace std;
int main()
{
    int q;
    cin>>q;
    while(q--)
    {
        int n,m;
        cin>>n>>m;
        int t,x,y;
        int l=m,r=m,time=0,flag=1;
        for(int i=1;i<=n;i++)
        {
            cin>>t>>x>>y;
            l-=(t-time);
            r+=(t-time);
            time=t;
            if(x>r||y<l) {flag=0;}//出现不满意直接标记
            l=max(l,x);//更换左右端点
            r=min(r,y);
        }
        if(flag) cout<<"YES"<<endl;
        else cout<<"NO"<<endl;
    }
    return 0;
}