滑窗模板_双向队列

附上电科算法讲堂  https://www.bilibili.com/video/av23189029?t=641  (感谢那些讲课的美好的人们)

/*
*  注:  还有少许细节问题可能需要注意: 例如 总长度小于窗口长度的情况.
*       和rGetMax  rGetMin 下标小于零的情况 没有pass.. 
*/

class HuaChuang_Max {
public:
    struct cnobe {
        int id;
        int val;
        cnobe () {}
        cnobe (int _id, int _val) : id(_id), val(_val) {}
    };
    
    deque<cnobe> cq;
    
    
    int GetMax(int date[], int ans[], int sz, int len) {  // [a, b] a>=1 开始滑窗 
        int cnt = 0;
        int i;
        while (!cq.empty()) cq.pop_back();
        for (i=1; i<len; ++i) {
            while (!cq.empty() && cq.back().val < date[i]) 
                    cq.pop_back();
            cq.push_back(cnobe(i, date[i]));
        }
        for (i=len; i<=sz; ++i) {
            while (!cq.empty() && cq.back().val < date[i]) 
                    cq.pop_back();
            cq.push_back(cnobe(i, date[i]));
            while (i - cq.front().id >= len) cq.pop_front();
            ans[cnt++] = cq.front().val;
        }
        return cnt;
    }
    
    int GetMin(int date[], int ans[], int sz, int len) {  // [a, b] a>=1 开始滑窗 
        int cnt = 0;
        int i;
        while (!cq.empty()) cq.pop_back();
        for (i=1; i<len; ++i) {
            while (!cq.empty() && cq.back().val > date[i]) 
                    cq.pop_back();
            cq.push_back(cnobe(i, date[i]));
        }
        for (i=len; i<=sz; ++i) {
            while (!cq.empty() && cq.back().val > date[i]) 
                    cq.pop_back();
            cq.push_back(cnobe(i, date[i]));
            while (i - cq.front().id >= len) cq.pop_front();
            ans[cnt++] = cq.front().val;
        }
        return cnt;
    }
    
    int rGetMax(int date[], int ans[], int sz, int len) {  // [a, b] a>=1 开始滑窗 
        int cnt = 0;
        int i;
        while (!cq.empty()) cq.pop_back();
        for (i=sz; i>sz-len+2 && i>0; --i) {
            while (!cq.empty() && cq.back().val < date[i]) 
                    cq.pop_back();
            cq.push_back(cnobe(i, date[i]));
        }
        for (i=sz-len+2; i>0; --i) {
            while (!cq.empty() && cq.back().val < date[i]) 
                    cq.pop_back();
            cq.push_back(cnobe(i, date[i]));
            while (cq.front().id - i >= len) cq.pop_front();
            ans[i] = cq.front().val;
            cnt++;
        }
        return cnt;
    }
    
    int rGetMin(int date[], int ans[], int sz, int len) {  // [a, b] a>=1 开始滑窗 
        int cnt = 0;
        int i;
        while (!cq.empty()) cq.pop_back();
        for (i=sz; i>sz-len+2 && i>0; --i) {
            while (!cq.empty() && cq.back().val > date[i]) 
                    cq.pop_back();
            cq.push_back(cnobe(i, date[i]));
        }
        for (i=sz-len+2; i>0; --i) {
            while (!cq.empty() && cq.back().val > date[i]) 
                    cq.pop_back();
            cq.push_back(cnobe(i, date[i]));
            while (cq.front().id - i >= len) cq.pop_front();
            ans[i] = cq.front().val;
            cnt++;
        }
        return cnt;
    }
}hc;