C++deque的用法

class Solution {
public:
    vector<int> maxInWindows(const vector<int>& num, unsigned int size) {
        vector<int> v;
        deque<int> dq;
        if(size > num.size() || !size) return v;
        for(int i = 0; i < num.size(); ++i) {
            while(!dq.empty() && num[dq.back()] < num[i]) dq.pop_back();
            dq.push_back(i);
            if(dq.front() + size <= i) dq.pop_front();
            if(i + 1 >= size)
                v.push_back(num[dq.front()]);
        }
        return v;
    }
};