算法之路(1) -- two sum

今天开始,打算每天写一道Leetcode上面的题目
开始呗...
另外,嗯..不知道有没有同学们有没有一块来刷leetcode的,组个队啊!

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].

解决方案一:

var twoSum = function(nums, target) {
    var map = new Map();
    var len = nums.length;
    for (let i = 0; i< len; i++) {
        map.set(nums[i], i);
    }
    
    var comp;
    for (let i = 0; i < len; i++) {
        comp = target - nums[i];
        if (map.has(comp) && map.get(comp) != i)
            return [i, map.get(comp)];
    }
    
    console.log("No two sum solution");
    
};


}

解决方案二:

第二种解决方案比第一种大约快了一倍的样子,很强.

var twoSum = function(nums, target) {
    var map = {};
    var len = nums.length;
    
    for (var i = 0; i < len; i++) {
        var complement = target - nums[i];
        var n = map[complement];
        
        if(n >= 0) {
            return [n, i];
        }
        map[nums[i]] = i;
    } 
    return undefined;
};