two-sum solution

Author: togo26

two-sum/togo26.js

@@ -0,0 +1,67 @@
+/**
+ * @param {number[]} nums
+ * @param {number} target
+ * @return {number[]}
+ */
+
+/*
+TC: O(n)
+SC: O(n) -> Map 사용
+*/
+
+var twoSum = function (nums, target) {
+  const map = new Map();
+  for (let i = 0; i < nums.length; i++) {
+    const complement = target - nums[i];
+    if (map.has(complement)) return [map.get(complement), i];
+    map.set(nums[i], i);
+  }
+};
+
+/*
+With two points
+TC: O(nlogn) -> sort 사용
+SC: O(n) -> origin index 배열 생성
+*/
+
+var twoSum = function (nums, target) {
+  const numsWithOriginIndex = nums.map((num, i) => [num, i]);
+  numsWithOriginIndex.sort(([a], [b]) => a - b);
+
+  let left = 0;
+  let right = nums.length - 1;
+  let result;
+
+  while (left < right) {
+    const [leftValue, leftIndex] = numsWithOriginIndex[left];
+    const [rightValue, rightIndex] = numsWithOriginIndex[right];
+    const sum = leftValue + rightValue;
+
+    if (sum === target) {
+      result = [leftIndex, rightIndex];
+      break;
+    }
+
+    if (sum > target) right--;
+    else left++;
+  }
+
+  return result;
+};
+
+/*
+Brute force
+TC: O(n^2)
+SC: O(1)
+*/
+
+var twoSum = function (nums, target) {
+  for (let i = 0; i < nums.length; i++) {
+    for (let j = i + 1; j < nums.length; j++) {
+      if (nums[i] + nums[j] === target) {
+        return [i, j];
+      }
+    }
+  }
+  return result;
+};