add: Combination Sum solution

Author: yoouyeon

combination-sum/yoouyeon.ts

@@ -0,0 +1,25 @@
+// [39] Combination Sum
+
+function combinationSum(candidates: number[], target: number): number[][] {
+  const n = candidates.length;
+  const output: number[][] = [];
+
+  function dfs(arr: number[], startIdx: number, sum: number) {
+    if (sum === target) {
+      output.push([...arr]);
+      return;
+    }
+    if (sum > target) return;
+
+    // 현재 숫자부터 다시 시작 (중복 선택이 가능하기 때문)
+    for (let idx = startIdx; idx < n; idx++) {
+      arr.push(candidates[idx]);
+      dfs(arr, idx, sum + candidates[idx]);
+      arr.pop();
+    }
+  }
+
+  dfs([], 0, 0);
+
+  return output;
+}