count_nice_pair.py (1027B)
| # 1814. Count Nice Pairs in an Array
import collections
"""
given an array 'nums' that consists of non-negative integers. let us define
'rev(x)' as the reverse of the non-negative integer 'x'. for example,
'rev(123) = 321' and 'rev(120) = 21'. a pair of indices '(i, j)' is nice if
it satisfies all of the following conditions: '0 <= i < j < nums.length' and
'nums[i] + rev(nums[j]) == nums[j] + rev(nums[i])'. return the number of nice
pairs of indices. since that number be very large, return it modulo 1e9+7
"""
class Solution(object):
def countNicePairs(self, nums):
"""
:type nums: List[int]
:rtype: int
"""
ans = 0
cnt = collections.Counter()
for i in nums:
b = int(str(i)[::-1])
ans += cnt[i - b]
cnt[i - b] += 1
return ans % (10**9 + 7)
if __name__ == "__main__":
obj = Solution()
print(obj.countNicePairs([42, 11, 1, 97])) # expect: 2
print(obj.countNicePairs([13, 10, 35, 24, 76])) # expect: 4
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