题目：

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.

示例：

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

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

原题链接：

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

解法①

/**
 * @param {number[]} nums
 * @param {number} target
 * @return {number[]}
 */
var twoSum = function(nums, target) {
    var result = [];
    for (var i = 0; i < nums.length; i++) {
        for (var j = i+1; j < nums.length; j++) {
            if (nums[i] + nums[j] === target && i !== j) {
                result[0] = i;
                result[1] = j;
                return result;
            }
        }
    }
    return result;
};

解法②

/**
 * @param {number[]} nums
 * @param {number} target
 * @return {number[]}
 */
var twoSum = function(nums, target) {
    var temp = [];
    for (var i = 0; i < nums.length; i++) {
        var cur = nums[i];
        if (temp[target - cur] !== undefined) {
            return [temp[target - cur], i];
        }
        temp[cur] = i;
    }
    return [];
};