220. Contains Duplicate III set的应用

Given an array of integers, find out whether there are two distinct indices i and j in the array such that the difference between nums[i] andnums[j] is at most t and the difference between i andj is at most k.

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分析：

在关系容器中有一类，set用来存可重复的的关系。

set有lower_bound(k)用来求不大于k的函数，以及upper_bound(k)用来求不小于k的的函数，很适合用来求此题。

注意代码若nums[i]与nums[j]不超过t，则nums[i]-nms[[j]<=t &&nums[j]-nums[i]<=t;

代码如下：

class Solution {
public:
    bool containsNearbyAlmostDuplicate(vector<int>& nums, int k, int t) {
        set<int> s1;
        if(nums.size()<2 || k<1)  return false;
        for(int i=0;i<nums.size();++i)
        {
            if(i>k) s1.erase(nums[i-k-1]);
            auto p=s1.lower_bound(nums[i]-t);
            if(p!=s1.end()&& ((*p-nums[i])<=t)) return true;
            s1.insert(nums[i]);
        }
        return false;
    }
};