Given an array of integers and an integer k, find out whether there are two distinct indices i and j in the array such that nums[i] = nums[j] and the difference between i and j is at most k.
分析
题目描述：给定一个整数序列，查找是否存在两个下标分别为；
定义一个长度最大为k的滑动窗口，用一个unordered_set维护窗口内的数字判断是否出现重复，使用两个指针。
AC代码
class Solution {
public:
bool containsNearbyDuplicate(vector<int>& nums, int k) {
if (nums.empty())
return false;
int sz = nums.size();
//使用容器unordered_set 其查找性能为常量
unordered_set<int> us;
int start = 0, end = 0;
for (int i = 0; i < sz; ++i)
{
if (us.count(nums[i]) == 0)
{
us.insert(nums[i]);
++end;
}
else{
return true;
}
if (end - start > k)
{
us.erase(nums[start]);
++start;
}
}//for
return false;
}
};