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Problem Solving/LeetCode

2023.11.22 Today's Challenge

fabichoi 2023. 11. 22. 23:45

https://leetcode.com/problems/count-nice-pairs-in-an-array/

 

Count Nice Pairs in an Array - LeetCode

Can you solve this real interview question? Count Nice Pairs in an Array - You are 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

leetcode.com

해쉬맵으로 푸는 문제

class Solution:
    def countNicePairs(self, nums: List[int]) -> int:
        def rev(num):
            res = 0
            while num:
                res = res * 10 + num % 10
                num //= 10
            return res

        arr = []
        for i in range(len(nums)):
            arr.append(nums[i] - rev(nums[i]))

        d = defaultdict(int)
        ans = 0
        MOD = 10 ** 9 + 7

        for num in arr:
            ans = (ans + d[num]) % MOD
            d[num] += 1
        
        return ans
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