solve: combination sum

Author: wogha95

combination-sum/wogha95.js

@@ -0,0 +1,84 @@
+// 2차
+// 몫을 활용하여 시간복잡도를 줄이고자 하였으나 generateSubResult에서 추가 시간발생으로 유의미한 결과를 발견하지 못했습니다.
+// TC: O(C^2 * T)
+// SC: O(T)
+// C: candidates.length, T: target
+
+/**
+ * @param {number[]} candidates
+ * @param {number} target
+ * @return {number[][]}
+ */
+var combinationSum = function (candidates, target) {
+  const result = [];
+  // 'q' means 'quotient'.
+  const qList = candidates.map((candidate) => Math.floor(target / candidate));
+
+  dfs([], 0);
+
+  return result;
+
+  function dfs(selectedQList, total) {
+    if (total > target) {
+      return;
+    }
+
+    if (total === target) {
+      result.push(generateSubResult(selectedQList));
+      return;
+    }
+
+    const currentIndex = selectedQList.length;
+    for (let q = qList[currentIndex]; q >= 0; q--) {
+      selectedQList.push(q);
+      dfs(selectedQList, total + candidates[currentIndex] * q);
+      selectedQList.pop();
+    }
+  }
+
+  function generateSubResult(selectedQList) {
+    return selectedQList
+      .map((q, index) => new Array(q).fill(candidates[index]))
+      .flat();
+  }
+};
+
+// 1차
+// dfs를 활용하여 각 요소를 추가 -> 재귀 -> 제거로 순회합니다.
+// TC: O(C^T)
+// SC: O(T)
+// C: candidates.length, T: target
+
+/**
+ * @param {number[]} candidates
+ * @param {number} target
+ * @return {number[][]}
+ */
+var combinationSum = function (candidates, target) {
+  const result = [];
+
+  dfs([], 0, 0);
+
+  return result;
+
+  function dfs(subResult, total, currentIndex) {
+    if (total > target) {
+      return;
+    }
+
+    if (total === target) {
+      result.push([...subResult]);
+      return;
+    }
+
+    if (currentIndex === candidates.length) {
+      return;
+    }
+
+    const candidate = candidates[currentIndex];
+    subResult.push(candidate);
+    dfs(subResult, total + candidate, currentIndex);
+    subResult.pop();
+    dfs(subResult, total, currentIndex + 1);
+  }
+};