1438. The longest continuous sub-array whose absolute difference does not exceed the limit (sliding window)

Why can I use a sliding window?

For a given interval [i,j] does not meet the requirements, then for the interval j'>j, [i,j'] does not meet the requirements, for i<i', [i',j], [i', j'] does not meet the requirements, i and j are monotonic.

Maintain a sliding window [i, j] to meet the requirements, in order to verify that [i, j] meets the requirements, we must maintain the maximum and minimum values ​​of a period of time. The most direct idea, use map<int,int> 

class Solution {
public:
    int longestSubarray(vector<int>& nums, int limit) {
        // 维护区间里的最大值以及最小值
        map<int,int> treeMap;
        int res = 0;
        for(int i=0,j=0;j<nums.size();j++){
            treeMap[nums[j]]++;
            while(abs(nums[j]-treeMap.begin()->first)>limit||abs(nums[j]-treeMap.rbegin()->first)>limit){
                treeMap[nums[i]]--;
                if(treeMap[nums[i]]==0){
                    treeMap.erase(nums[i]);
                }
                i++;
            }
            res = max(res,j-i+1);
        }
        return res;
    }
};

You can also use a monotonic queue to maintain the maximum and minimum values ​​in the interval. This practice is left for consideration.