solve: two sum

Author: wogha95

two-sum/wogha95.js

@@ -0,0 +1,51 @@
+// 2차: index를 값으로 갖는 Map을 활용하여 한번의 순회로 답안 도출
+// TC: O(N)
+// SC: O(N)
+
+/**
+ * @param {number[]} nums
+ * @param {number} target
+ * @return {number[]}
+ */
+var twoSum = function (nums, target) {
+  const valueIndexMap = new Map();
+
+  for (let index = 0; index < nums.length; index++) {
+    const value = nums[index];
+    const anotherValue = target - value;
+
+    if (valueIndexMap.has(anotherValue)) {
+      return [index, valueIndexMap.get(anotherValue)];
+    }
+
+    valueIndexMap.set(value, index);
+  }
+};
+
+// 1차: 정렬 후 투포인터 활용
+// TC: O(N * logN)
+// SC: O(N)
+
+/**
+ * @param {number[]} nums
+ * @param {number} target
+ * @return {number[]}
+ */
+var twoSum = function (nums, target) {
+  const sortedNums = nums
+    .map((value, index) => ({ value, index }))
+    .sort((a, b) => a.value - b.value);
+  let left = 0;
+  let right = sortedNums.length - 1;
+
+  while (left < right) {
+    const sum = sortedNums[left].value + sortedNums[right].value;
+    if (sum < target) {
+      left += 1;
+    } else if (sum > target) {
+      right -= 1;
+    } else {
+      return [sortedNums[left].index, sortedNums[right].index];
+    }
+  }
+};