1.TwoSum.md

1. Two Sum

Given an array of integers nums and an integer target, return indices of the two numbers such that they add up to target.
You may assume that each input would have exactly one solution, and you may not use the same element twice.
You can return the answer in any order.

Example 1:

Input: nums = [2,7,11,15], target = 9
Output: [0,1]
Output: Because nums[0] + nums[1] == 9, we return [0, 1].

Example 2:

Input: nums = [3,2,4], target = 6
Output: [1,2]

Example 3:

Input: nums = [3,3], target = 6
Output: [0,1]

Constraints:

• 2 <= nums.length <= 103
• -109 <= nums[i] <= 109
• -109 <= target <= 109
• Only one valid answer exists.

Solutions

• java

/*
 Success Detail:
 Runtime: 0 ms, faster than 100.00% of Java online submissions for Two Sum.
 Memory Usage: 39 MB, less than 84.50% of Java online submissions for Two Sum.
 */
class Solution {
    public int[] twoSum(int[] nums, int target) {
        Map<Integer, Integer> map = new HashMap<>();
        for (int i = 0; i < nums.length; i++) {
            int num = nums[i];
            if (map.containsKey(target - num)) {
                return new int[]{i, map.get(target - num)};
            }
            map.put(num, i);
        }
        throw new IllegalArgumentException("no two sum solution");
    }
}

• javascript

/*
Success Detail:
Runtime: 80 ms, faster than 76.86% of JavaScript online submissions for Two Sum.
Memory Usage: 38.8 MB, less than 72.89% of JavaScript online submissions for Two Sum.
 */
/**
 * @param {number[]} nums
 * @param {number} target
 * @return {number[]}
 */
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];
            }
        }
    }
};