g0001_0100.s0039_combination_sum.Solution.kt Maven / Gradle / Ivy

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Kotlin-based LeetCode algorithm problem solutions, regularly updated

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package g0001_0100.s0039_combination_sum

// #Medium #Top_100_Liked_Questions #Array #Backtracking #Algorithm_II_Day_10_Recursion_Backtracking
// #Level_2_Day_20_Brute_Force/Backtracking #Udemy_Backtracking/Recursion
// #Big_O_Time_O(2^n)_Space_O(n+2^n) #2023_07_05_Time_226_ms_(88.89%)_Space_38.1_MB_(94.95%)

class Solution {
    fun combinationSum(candidates: IntArray, target: Int): List> {
        val result = mutableListOf>()
        fun backtrack(start: Int, case: MutableList, sum: Int) {
            if (sum >= target) {
                if (sum == target) {
                    result.add(case.toList())
                }
                return
            }
            for (i in start until candidates.size) {
                case.add(candidates[i])
                backtrack(i, case, sum + candidates[i])
                case.removeAt(case.size - 1)
            }
        }
        backtrack(0, mutableListOf(), 0)
        return result
    }
}