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
SOLUTION:
class Solution:
def numIdenticalPairs(self, nums: List[int]) -> int:
n = len(nums)
valIndexes = {}
total = 0
for i in range(n):
valIndexes[nums[i]] = valIndexes.get(nums[i], 0) + 1
for val in valIndexes:
freq = valIndexes[val]
total += freq * (freq - 1) // 2
return total
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