剑指offer-滑动窗口的最大值

 1 class Solution {
 2 public:
 3     vector<int> maxInWindows(const vector<int>& num, unsigned int size)
 4     {
 5         vector<int> v;
 6         if(num.size()>=size&&size>=1){
 7             deque<int> index;
 8             //队列中保留第一个窗口的最大值下标
 9             for(int i=0;i<size;i++){
10                 while(!index.empty()&&num[i]>=num[index.back()])
11                     index.pop_back();
12                 index.push_back(i);
13             }
14             for(int i=size;i<num.size();i++){
15                 v.push_back(num[index.front()]);
16                 while(!index.empty()&&num[i]>=num[index.back()])
17                     index.pop_back();
18                 if(!index.empty()&&index.front()<=i-size)
19                     index.pop_front();
20                 index.push_back(i);
21             }
22             v.push_back(num[index.front()]);
23         }
24         return v;
25     }
26 };