릿코드 1814. Count Nice Pairs in an Array 코틀린

1번풀이:이중루프로 하나씩 비교해서 만족하면 리턴

import kotlin.math.pow

class Solution {
    fun countNicePairs(nums: IntArray): Int {
        val numList = nums.toList().sorted()
        var res = 0
        for ((iIndex,iValue) in numList.withIndex()){
            for ((jIndex,jValue) in numList.withIndex()){
                if (iIndex==jIndex){
                    continue
                }
                val reverseIValue = iValue.toString().reversed().toInt()
                val reverseJValue = jValue.toString().reversed().toInt()
                if (iValue+reverseJValue==reverseIValue+jValue){
                    //println("""${iValue} : ${jValue}""")
                    res+=1
                }
            }
        }
        res=res/2
        //println(res)
        val modNum=10.0.pow(9).toInt()
        return res % (modNum+7)
    }
}

당연히 타임아웃

 

2번풀이:nums[i] + rev(nums[j]) == nums[j] + rev(nums[i])->nums[i] - rev(nums[i]) == nums[j] - rev(nums[j])
니까
for돌려서 현재 nums[i] - rev(nums[i]) 값을 맵에 담아두고 다시 for돌려서 같은값마다 조합갯수연산

import kotlin.math.pow

class Solution {
    fun countNicePairs(nums: IntArray): Int {
        val numList = nums.toList().sorted()
        val reverseMinusList= mutableListOf<Long>()
        var res:Int = 0

        for (i in numList){
            val reverseIValue = i.toString().reversed().toLong()
            reverseMinusList.add(i-reverseIValue)
        }
        val numHashMap = HashMap<Long, Int>()
        for (i in reverseMinusList){
            numHashMap[i]=numHashMap[i]?.plus(1)?:1
        }
        //println(numHashMap)
        for ((key,value) in numHashMap){
            //println("""${key}  :  ${value}  = ${combinationCount(value)}""")

            res+=combinationCount(value)
        }

        //println(res)
        val modNum=10.0.pow(9).toInt()
        println(4999950000%(modNum+7))
        return res % (modNum+7)
    }
    private fun combinationCount(inputInt:Int):Int{
        var res=0
        for(i in 0 until inputInt){
            res+=i
        }
        return res
    }



}

?? 84/85나오는데 조합연산에서 틀린거같음

테케중 맵에 0이 100000개있는거에서 맵은 정확히 들어가는거같은데  100000C2하는데서 틀린듯

 

정답

class Solution {
    fun countNicePairs(nums: IntArray): Int {
        var res = 0
        val mod = 1e9.toInt() + 7
        var map: HashMap<Int, Int> = HashMap<Int, Int>()
        for(num in nums) {
            val diff = num - getReverse(num)
            val count = map.getOrDefault(diff, 0)
            map.put(diff, count + 1)
            res = (res + count) % mod
        }
        return res
    }
    
    fun getReverse(n: Int): Int {
        var rem = 0
        var num = n
        while(num > 0) {
            rem = (rem * 10) + (num % 10)
            num /= 10
        }
        return rem
    }
}