2364.js

/** ------------------------------------------------------------------------------
 * 
 * 2364. Count Number of Bad Pairs
 * Topics: Array, Hash Table
 * https://leetcode.com/problems/count-number-of-bad-pairs/description/
 * 
 ------------------------------------------------------------------------------ */
/**
 * @param {number[]} nums
 * @return {number}
 */
var countBadPairs = function (nums) {
  let res = 0
  let map = new Map()
  let n = (nums.length * (nums.length - 1)) / 2
  for (let i = 0; i < nums.length; i++) {
    if (map.has(nums[i] - i)) {
      res += map.get(nums[i] - i)
      map.set(nums[i] - i, map.get(nums[i] - i) + 1)
    } else {
      map.set(nums[i] - i, 1)
    }
  }
  // console.log(res);
  return n - res
}

console.log(countBadPairs([4, 1, 3, 3]))
// console.log(countBadPairs([1, 2, 3, 4, 5]))