feat: two sum

Author: minji-go

two-sum/minji-go.java

@@ -0,0 +1,21 @@
+/*
+    Problem: https://leetcode.com/problems/two-sum/
+    Description: return indices of the two numbers such that they add up to target. not use the same element twice.
+    Topics: Array, Hash Table
+    Time Complexity: O(N), Runtime 2ms
+    Space Complexity: O(N), Memory 45.1MB
+*/
+class Solution {
+    public int[] twoSum(int[] nums, int target) {
+        Map<Integer, Integer> numIndex = new HashMap<>();
+        for(int secondIndex=0; secondIndex<nums.length; secondIndex++){
+            if(numIndex.containsKey(target-nums[secondIndex])){
+                int firstIndex = numIndex.get(target-nums[secondIndex]);
+                return new int[]{firstIndex, secondIndex};
+            } else {
+                numIndex.put(nums[secondIndex], secondIndex);
+            }
+        }
+        return new int[]{};
+    }
+}