LeetCode - 1 - Two sum
/**
* @param {number[]} nums
* @param {number} target
* @return {number[]}
*/
var twoSum = function(nums, target) {
let r = {};
for (let j=0;j<nums.length;j++){
let left = target - nums[j];
if (r[left] === undefined) {
r[nums[j]] = j;
} else {
return [r[left], j];
}
}
};