Method countBadPairs

CountNumberOfBadPairs.java:2–14

(int[] nums)

class Solution {
    public long countBadPairs(int[] nums) {
        long n = nums.length;
        long goodPairs=0;
        long totalPairs = n*(n-1)/2;
        HashMap<Integer,Integer> map = new HashMap<>();
        for(int i=0;i<n;i++){
           int val = i - nums[i];
           int prevCount = map.getOrDefault(val,0);
           goodPairs += prevCount;
           map.put(val, map.getOrDefault(val,0)+1);
        }
        return totalPairs - goodPairs;
    }
}