Failing leet code next-permutation test cases but works on local system

Question

I was attempting the leet-code problem next permutation and here's my js soln.

/**
 * @param {number[]} nums
 * @return {void} Do not return anything, modify nums in-place instead.
 */
var nextPermutation = function(nums) {

    for(let i=nums.length-1;i>=0;i--){
        if(nums[i]>nums[i-1]){
            var x= [...nums.slice(0,i-1),nums[i],nums[i-1]]
            console.log(x)// <- This gives a different value as compared to 
            return x//          the returned value 
        }
    }
    return nums.reverse()
    
};

The issue is that I am pretty much failing every test case on leetcode and the printed values are absolutely correct whereas the returned values are incorrect. It gets weirder as it runs exactly as expected on my local system with node.js. Is this an issue with leetcode? I'd really appreciate if someone could try running this on leetcode on their local system.

Answer 1

So for each number sequence, we need to find the next bigger one by swapping digits. That's awesome lets try. The hardest part was to define the algorithm. Here's how I did it:

/*
Instruction

start with 2nd digit from right
swap with next smallest to the right
if result is bigger than exit that's the solution

start with 3rd digit from right
if exists, swap with next smallest to the right, sort to the right. solution

start with 4rd digit from right
if exists, swap with next smallest to the right, sort to the right. solution

return first number (minimal)
*/

And here's my solution:

/**
 * @param {number[]} nums
 * @return {void} Do not return anything, modify nums in-place instead.
 */
var nextPermutation = function (nums) {

    function swap(index1, index2) {
        var temp = nums[index1]
        nums[index1] = nums[index2]
        nums[index2] = temp;
    }

    function next_bigger_from(pos) {
        var current = nums[pos];
        result = -1;
        var min = Infinity;
        for (var i = pos + 1; i < len; i++) {
            if (nums[i] > current && nums[i] < Infinity) {
                result = i;
                min = nums[i];
            }
        }
        return result;
    }

    function sort_from(pos) {
        for (var i = pos; i < len - 1; i++) {
            for (var j = i + 1; j < len; j++) {
                if (nums[i] > nums[j]) {
                    swap(i, j)
                }
            }
        }
    }

    var len = nums.length;
    

    if (len < 2) {
        console.log("" + nums)
        return;
    }

    var rotator = 2; // from right
    while (rotator <= len) {
        var pos = len - rotator;
        var pos2 = next_bigger_from(pos);
        if (pos2 == -1) {
            rotator += 1;
            continue;
        }
        swap(pos, pos2);
        sort_from(pos+1);
        console.log("" + nums)
        return;
    }
  
  nums = nums.sort();  
    console.log("" + nums)
    return;
};

nextPermutation([1, 2, 3])
nextPermutation([3, 2, 1])
nextPermutation([1, 1, 5])

var nums = [1, 3, 5, 7];
for (var i = 0; i < 24; i++) {
  nextPermutation(nums)

}

.as-console-wrapper {
  max-height: 100% !important;
  top: 0;
}

So what is wrong with the following solution by the OP? It doesn't change the array nums but rather returns an array x. This is why the second test (of the 4 digits sequence) fails for your code. By the way, even if I try nums = nextPermutation(nums) for the second test the results are still wrong.

/**
 * @param {number[]} nums
 * @return {void} Do not return anything, modify nums in-place instead.
 */
var nextPermutation = function(nums) {

  for (let i = nums.length - 1; i >= 0; i--) {
    if (nums[i] > nums[i - 1]) {
      var x = [...nums.slice(0, i - 1), nums[i], nums[i - 1]]
      console.log("" + x) // <- This gives a different value as compared to 
      return x //          the returned value 

    }
  }

  console.log("" + nums.reverse()) // added for verbosity
  return nums.reverse()

};


nextPermutation([1, 2, 3])
nextPermutation([3, 2, 1])
nextPermutation([1, 1, 5])

var nums = [1, 3, 5, 7];
for (var i = 0; i < 24; i++) {
  nextPermutation(nums)
}