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# 題目敘述
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
# 解題思路
# Solution
import java.util.HashMap; | |
import java.util.Map; | |
class Solution { | |
public int numIdenticalPairs(int[] nums) { | |
Map<Integer, Integer> map = new HashMap<>(); | |
for(int num : nums){ | |
map.put(num, map.getOrDefault(num, 0) + 1); | |
} | |
int ans = 0; | |
for(int key : map.keySet()){ | |
for(int i = map.get(key) - 1; i > 0; i--){ | |
ans += i; | |
} | |
} | |
return ans; | |
} | |
} |
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