Problems

Given an array of integers, return indices of the two numbers such that they add up to a specific target.

You may assume that each input would have exactly one solution, and you may not use the same element twice.

Example:
Given nums = [2, 7, 11, 15], target = 9,

Because nums[0] + nums[1] = 2 + 7 = 9,
return [0, 1].

Solution

var twoSum = function(nums, target) {
    var r = [];
    for(var i=0; i<nums.length; i++) {
        for(var j=i+1; j<nums.length; j++) { // Only loop the element only after i
            if(nums[j] === target - nums[i]) {
                r.push(i, j);
            }
        }
    }
    return r;
};