1512. Number of Good Pairs
EasyLeetCodeGiven 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.
Constraints:
1 <= nums.length <= 100
1 <= nums[i] <= 100
How to solve the problem
Using nested for loop, the second loop range equals i + 1 to length of nums.
Code
Python
class Solution:
def numIdenticalPairs(self, nums: List[int]) -> int:
count = 0
for i in range(len(nums)):
for j in range(i+1, len(nums)):
if nums[i] == nums[j]:
count += 1
return count
Complexity
Time complexity: O(n^2)
Nested loop is needed.
Space complexity: O(1)
No extra data structures are used.
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