README.md

1512. Number of Good Pairs

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

Solutions (Ruby)

1. Count

# @param {Integer[]} nums
# @return {Integer}
def num_identical_pairs(nums)
    cnt = [0] * 101
    ret = 0

    for num in nums
        ret += cnt[num]
        cnt[num] += 1
    end

    return ret
end

Solutions (Rust)

1. Count

impl Solution {
    pub fn num_identical_pairs(nums: Vec<i32>) -> i32 {
        let mut cnt = [0; 101];
        let mut ret = 0;

        for num in nums {
            ret += cnt[num as usize];
            cnt[num as usize] += 1;
        }

        ret
    }
}