Time: 9 ms (78.22%), Space: 38.8 MB (56.69%) - LeetHub

Author: hajin-kim

0046-permutations/0046-permutations.kt

@@ -0,0 +1,32 @@
+class Solution {
+    private fun backtrack(
+        nums: IntArray,
+        result: MutableList<List<Int>>,
+        used: BooleanArray,
+        current: MutableList<Int>,
+    ) {
+        if (current.size == nums.size) {
+            result += current
+            return
+        }
+        for (i in nums.indices) {
+            if (used[i]) {
+                continue
+            }
+
+            used[i] = true
+            val next = current.toMutableList()
+            next += nums[i]
+            backtrack(nums, result, used, next)
+            used[i] = false
+        }
+    }
+
+    fun permute(nums: IntArray): List<List<Int>> {
+        val result = mutableListOf<List<Int>>()
+        val used = BooleanArray(nums.size)
+
+        backtrack(nums, result, used, mutableListOf())
+        return result
+    }
+}