C. Vasya and String
time limit per test 1 second
memory limit per test 256 megabytes
input standard input
output standard output
High school student Vasya got a string of length n as a birthday present. This string consists of letters 'a' and 'b' only. Vasya denotesbeauty of the string as the maximum length of a substring
Vasya can change no more than k
Input
The first line of the input contains two integers n and k (1 ≤ n ≤ 100 000, 0 ≤ k ≤ n) — the length of the string and the maximum number of characters to change.
The second line contains the string, consisting of letters 'a' and 'b' only.
Output
Print the only integer — the maximum beauty of the string Vasya can achieve by changing no more than k
Examples
input
4 2
abba
output
4
input
8 1
aabaabaa
output
5
Note
In the first sample, Vasya can obtain both strings "aaaa" and "bbbb".
In the second sample, the optimal answer is obtained with the string "aaaaabaa" or with the string "aabaaaaa".
题解：
有一个长度为n的字符串，这个字符串只含有a和b，你可以改变最多k次，问你连续最长的一样的字符串是多长？
从头到尾都遍历-->枚举-->改变 ，贪心最长度。 有点像二分
AC代码：
#include<bits/stdc++.h>
using namespace std;
const int N = 1e5+10;
int n,k;
int f(string s)
{
int l=0,r=-1;
int num=0;
int res=0;
while(++r<s.size())
{
if(s[r]=='b')
num++;
if(num>k)
{
while(s[l++]=='a');
num--;
}
res=max(res,r-l+1);
}
return res;
}
int main()
{
//freopen("in.txt","r",stdin);
//freopen("out.txt","w",stdout);
string s;
cin>>n>>k;
cin>>s;
int ans=f(s);
for(int i=0;i<s.size();i++)
s[i]='a'+'b'-s[i];
ans=max(ans,f(s));
cout<<ans<<endl;
return 0;
}
