Javascript 中的两个 Sum Leetcode - 代码看起来正确但 Leetcode 说它是错误的

Question

I'm working on the 'Two Sum' problem in Leetcode .

I'm sure this code is correct, I've tested it in Repl and it looks correct there, but Leetcode is giving me an error.

Here's my code:

var arr = [];

var twoSum = function(nums, target) {
   for(var i = 0; i < nums.length; i++){
        for(var j = i+1; j < nums.length; j++){
            console.log(nums[i] + ', ' + nums[j]);
            var tot = nums[i] + nums[j];        
            if(tot === target){
                arr.push(i,j);
                console.log(arr);
                return arr;
            }     
         }         
   }
};

//var a = [2, 7, 11, 15];
//var b = 9;
var a = [2, 3, 4];
var b = 6;

twoSum(a, b);

The error I'm getting is as follows:

Input:
[3,2,4]
6
Output:
[0,1,1,2]
Expected:
[1,2]

Why is it expecting [1, 2] ? Surely it should expect [0, 1] in this case, and then why is my code adding to the arr array twice? It looks like a bug to me...

Note: I see there's many posts about this problem on Leetcode, but none address the specific issue I have run into in Javascript.

Answer 1

Why is it expecting [1, 2]?

Because 2 + 4 = 6

Surely it should expect [0, 1] in this case

No, because 3 + 2 = 5

and then why is my code adding to the arr array twice?

Because you declared the array outside of the function. It is being re-used for every call to the function. Move the array declaration into your twoSum function or even better: Simply return [i, j] instead of push ing into the empty array.

Answer 2

Here is another solution you can try...

var twoSum = function(nums, target) {
let map = {};
for (let i = 0; i < nums.length; i++) {
  let compliment = target - nums[i];
  if (map[compliment]) {
    return [(map[compliment] - 1), i];
  } else {
    map[nums[i]] = i + 1;
    }
   }
 };

 twoSum([2, 3, 4],6);

Click Here to RUN

Answer 3

Here is an optimum solution

 /** * @param {number[]} nums * @param {number} target * @return {number[]} */ function twoSum(nums, target) { const numsObjs = {}; // create nums obj with value as key and index as value eg: [2,7,11,15] => {2: 0, 7: 1, 11: 2, 15: 3} for (let i = 0; i < nums.length; i++) { const currentValue = nums[i]; if (target - currentValue in numsObjs) { return [i, numsObjs[target - currentValue]]; } numsObjs[nums[i]] = i; } return [-1, -1]; } console.log(twoSum([2, 7, 11, 15], 9))