[ PS ] : Combination Sum

Author: uraflower

combination-sum/uraflower.js

@@ -0,0 +1,44 @@
+/**
+ * 주어진 배열의 원소 조합(중복 허용)의 합이 target인 모든 경우를 반환하는 함수
+ * @param {number[]} candidates
+ * @param {number} target
+ * @return {number[][]}
+ */
+const combinationSum = function(candidates, target) {
+    const sortedCandidates = candidates.filter((x) => x <= target).sort((a, b) => Number(a) - Number(b));
+    const answer = [];
+    
+    if (sortedCandidates.length === 0) {
+        return answer;
+    }
+
+    function search(currentIdx, combination, total) {
+        if (total === target) {
+            answer.push([...combination]); // 배열 자체를 넣으면 참조 때문에 값이 변경되므로, 복사해서 넣어야 함
+            return;
+        }
+
+        if (total > target) {
+            return; // backtracking
+        }
+
+        combination.push(sortedCandidates[currentIdx]);
+        search(currentIdx, combination, total + sortedCandidates[currentIdx]);
+        combination.pop();
+
+        if (total + sortedCandidates[currentIdx] > target) {
+            return; // backtracking
+        }
+
+        if (currentIdx + 1 < sortedCandidates.length) {
+            search(currentIdx + 1, combination, total);
+        }
+    }
+
+    search(0, [], 0);
+    return answer;
+};
+
+// t: target
+// 시간복잡도: O(2^t)
+// 공간복잡도: O(t)