1512-NumberOfGoodPairs.go

package main

// 1512. Number of Good Pairs
// Given an array of integers nums, return the number of good pairs.
// A pair (i, j) is called good if nums[i] == nums[j] and i < j.

// 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

import "fmt"

func numIdenticalPairs(nums []int) int {
    res := 0
    for i := 0; i < len(nums); i++ {
        for j := i + 1; j < len(nums); j++ {
            // 如果一组数字 (i,j) 满足 nums[i] == nums[j] 且 i < j ，就可以认为这是一组 好数对
            if nums[i] == nums[j] {
                res++
            }
        }
    }
    return res
}

func main() {
    // There are 4 good pairs (0,3), (0,4), (3,4), (2,5) 0-indexed.
    fmt.Println(numIdenticalPairs([]int{1,2,3,1,1,3})) // 4
    fmt.Println(numIdenticalPairs([]int{1,1,1,1})) // 6
    fmt.Println(numIdenticalPairs([]int{1,2,3})) // 0
}