docs: update 39. Combination Sum

Author: HC-kang

combination-sum/HC-kang.ts

@@ -0,0 +1,19 @@
+// T.C: O(n^t) // n: candidates.length, t: target
+// S.C: O(n)
+function combinationSum(candidates: number[], target: number): number[][] {
+  const result: number[][] = [];
+  function dfs(start: number, target: number, path: number[]) {
+    if (target < 0) return;
+    if (target === 0) {
+      result.push([...path]);
+      return;
+    }
+    for (let i = start; i < candidates.length; i++) {
+      path.push(candidates[i]);
+      dfs(i, target - candidates[i], path);
+      path.pop();
+    }
+  }
+  dfs(0, target, []);
+  return result;  
+};