题解 | #JZ59 滑动窗口的最大值#

public:
    vector<int> maxInWindows(const vector<int>& num, unsigned int size) {
        vector<int> ret;
        int len = num.size();
        
        if (len == 0 || size > len || size == 0) return ret;
        
        deque<int> dq;
        for (int i=0; i!=len; ++i) {
            if (dq.size() && i == dq.front()+size) dq.pop_front();    //队列头在窗口外失效移除
            
            while (dq.size() && num[dq.back()] < num[i]) dq.pop_back();    //从后向前移除队列中小于当前值的项，保持递减数列
            
            dq.push_back(i);    //压入当前值
            
            if (i >= size-1) ret.push_back(num[dq.front()]);    //压入窗口最大值
        }
        
        return ret;
    }
};