# ---
# title: 1512. Number of Good Pairs
# id: problem1512
# author: Tian Jun
# date: 2020-10-31
# difficulty: Easy
# categories: Array, Hash Table, Math
# link: <https://leetcode.com/problems/number-of-good-pairs/description/>
# hidden: true
# ---
# 
# Given an array of integers `nums`.
# 
# A pair `(i,j)` is called _good_ if `nums[i]` == `nums[j]` and `i` < `j`.
# 
# Return the number of _good_ pairs.
# 
# 
# 
# **Example 1:**
# 
#     
#     
#     Input: nums = [1,2,3,1,1,3]
#     Output: 4
#     Explanation: There are 4 good pairs (0,3), (0,4), (3,4), (2,5) 0-indexed.
#     
# 
# **Example 2:**
# 
#     
#     
#     Input: nums = [1,1,1,1]
#     Output: 6
#     Explanation: Each pair in the array are _good_.
#     
# 
# **Example 3:**
# 
#     
#     
#     Input: nums = [1,2,3]
#     Output: 0
#     
# 
# 
# 
# **Constraints:**
# 
#   * `1 <= nums.length <= 100`
#   * `1 <= nums[i] <= 100`
# 
# 
## @lc code=start
using LeetCode

## add your code here:
## @lc code=end
