Problem:
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.
Summary:
给出数组nums，整型数k，找到数组中是否存在nums[i]和nums[j]相等且i - j小于k的情况。
Solution:
开始用最简单写法，两重for循环逐一查找，出现TLE。
后用HashMap改进，key为数组中出现的数字，value为最近出现位置的下标。
class Solution {
public:
bool containsNearbyDuplicate(vector<int>& nums, int k) {
int len = nums.size();
unordered_map<int, int> m;
for (int i = ; i < len; i++) {
if (m.find(nums[i]) != m.end() && i - m[nums[i]] <= k) {
return true;
}
else {
m[nums[i]] = i;
}
}
return false;
}
};