Leetcode (1) Sum

https://leetcode.com/problems/two-sum/

Given an array of integers, find the numbers such that they add up to a specific target number.

The function twosum should return indices of the numbers such that they add up to the target, where index1 must is Les S than Index2. Please note that your returned answers (both Index1 and INDEX2) is not zero-based.

You may assume this each input would has exactly one solution.

Input:numbers={2, 7, one, A, target=9
Output:index1=1, index2=2

Today starts from the zero single row Leetcode, commemorates some

This is a simple question, but there are several details to note. This problem requires the return of the subscript, note is starting from 1.

Solution One: Double pointer brute force solution, Time Complexity O (n2), Space O (1)

 Public classSolution { Public int[] Twosum (int[] Nums,inttarget) {        int[] res =New int[2];  for(inti = 0; i < nums.length-1; i++){             for(intj = i+1; J < Nums.length; J + +){                if(Nums[i]+nums[j] = =target) {res[0] = i+1; res[1] = j+1;  Break; }            }        }        returnRes; }}

Solution 2:hashtable, Time complexity O (n), Spatial complexity O (1)

 Public classSolution { Public int[] Twosum (int[] Nums,inttarget) {        int[] res =New int[2]; Map<integer, integer> map =NewHashmap<>();  for(inti = 0; i < nums.length; i++){            if(Map.containskey (Nums[i])) {res[0] = Map.get (Nums[i]) +1; res[1] = i+1;  Break; }Else{map.put (target-Nums[i], i); }        }        returnRes; }}

Leetcode (1) Sum