# 2364. Count Number of Bad Pairs
###### tags: `Leetcode` `Medium` `HashMap`
Link: https://leetcode.com/problems/count-number-of-bad-pairs/description/
## 思路
和[1814. Count Nice Pairs in an Array](https://hackmd.io/c8Ipq2IPRyiaZqYRaz69yw)很像

## Code

class Solution {
public long countBadPairs(int[] nums) {
long ans = 0;
Map<Integer, Integer> map = new HashMap<>();
for(int i=0; i<nums.length; i++){
ans += i-map.getOrDefault(nums[i]-i, 0);
map.put(nums[i]-i, map.getOrDefault(nums[i]-i, 0)+1);
}
return ans;
}
}