problem:2379. 得到 K 个黑块的最少涂色次数

思路：定长滑动窗口模板题

Accode:

class Solution {
public:
    int minimumRecolors(string blocks, int k) {
        deque<char> deq;
        int cnt = 0;
        for(int i=0;i<blocks.length();i++){
            if(deq.size() && i-deq.front()+1>k) deq.pop_front();
            if(blocks[i]=='B') deq.push_back(i);
            if(i+1>=k){
                cnt = max(cnt,(int)deq.size());
            }
        }
        return k-cnt;
    }
};

时间复杂度：$o(n)$