Solution for Combination Sum #254

Author: dohyeon2

combination-sum/dohyeon2.java

@@ -0,0 +1,30 @@
+import java.util.ArrayList;
+import java.util.List;
+
+class Solution {
+    // TC : O(n!) => TC : O(2^T)
+    // SC : O(n^2) => SC : O(T)
+    ArrayList<List<Integer>> result = new ArrayList<>();
+
+    public List<List<Integer>> combinationSum(int[] candidates, int target) {
+        backtrack(0, target, candidates, new ArrayList<>());
+        return result;
+    }
+
+    private void backtrack(int start, int diff, int[] candidates, ArrayList<Integer> path) {
+        if (diff == 0) {
+            result.add(new ArrayList<>(path)); // 깊은 복사
+            return;
+        }
+
+        if (diff < 0) {
+            return;
+        }
+
+        for (int i = start; i < candidates.length; i++) {
+            path.add(candidates[i]);
+            backtrack(i, diff - candidates[i], candidates, path);
+            path.remove(path.size() - 1);
+        }
+    }
+}