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剑65-滑动窗口的最大值
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剑65-滑动窗口的最大值
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题目描述
给定一个数组和滑动窗口的大小,找出所有滑动窗口里数值的最大值。
例如,如果输入数组{2,3,4,2,6,2,5,1}及滑动窗口的大小3,那么一共存在6个滑动窗口,
他们的最大值分别为{4,4,6,6,6,5}; 针对数组{2,3,4,2,6,2,5,1}的滑动窗口有以下6个:
{[2,3,4],2,6,2,5,1}, {2,[3,4,2],6,2,5,1}, {2,3,[4,2,6],2,5,1}, {2,3,4,[2,6,2],5,1}, {2,3,4,2,[6,2,5],1}, {2,3,4,2,6,[2,5,1]}。
////总的时间复杂度为O(n),获取最大值的时间复杂度为O(1)
class Solution {
public:
vector<int> maxInWindows(const vector<int>& num, unsigned int size)
{
vector<int> result;
if(num.size() >= size && size >= 1){
deque<int> IndexDeque;
for(int i = 0; i < size; i++){
while(!IndexDeque.empty() && num[i] >= num[IndexDeque.back()])
IndexDeque.pop_back();
IndexDeque.push_back(i);
}
for(int i = size; i < num.size(); i++){
result.push_back(num[IndexDeque.front()]);
while(!IndexDeque.empty() && num[i] >= num[IndexDeque.back()])
IndexDeque.pop_back();
if(!IndexDeque.empty() && IndexDeque.front() <= (int)(i - size))
IndexDeque.pop_front();
IndexDeque.push_back(i);
}
result.push_back(num[IndexDeque.front()]);
}
return result;
}
};