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Answer shows different even though the output is coming correctly

I was practicing some leetcode and I am pretty new to it. So, there is this problem where you need to shift the 0s to the right. I wrote the code and the output is coming as expected but the results yields []. Can anyone explain what's wrong? Here is the snippet of my code.enter image description here

And here is the result.

enter image description here

As you can clearly see in the stdout, the output is correct but the answer is coming as an empty list. What am I doing wrong? I appreciate your help. Thanks.

Solution

  • Ok, The question is based on Inplace operations and your logic is quite correct. I will explain with 3 things so it will be clear to you.

    1. Good programming practice:-

    The output yields [], because there is clear statement in 19th line

    //19 nums.clear();
//20 nums=nonZeroArray;

    Idea:- nums is cleared. contents of nonZeroArray is copied to nums.

    Actual thing:- But in this case if we use clear, then result will be cleared i.e [] and 20th line is not having any impact.

    Proof:- ->As the question is in place traversal, don't use clear statement. This is bad programming practice. Instead of 19th and 20th line you can try this

    for(int i=0; i<nums.length; i++)
{
   nums[i]=nonZeroArray[I];
}

    Don't use clear, instead of that copy element by element you will get result.

    2. Logic correction:- Even after doing this, you will get error because there is logic error in code.

    The question says if array is [0,1,0,3,12]. The output should be [1,3,12,0,0]. pushing zeros to end.

    In line 2, no need of sort function. suppose take example of arr=[0,2,1]. the output should be [2,1,0]. if we sort in line 2, then output will be [1,2,0] which is wrong. so don't sort.

    The final corrected code will be:-

    class Solution {
 void moveZeroes(List<int> nums) {
    List<int> nonZeroArray=[];
    for(int i=0; i<nums.length; i++){
      if(nums[i]!=0){
          nonZeroArray.add(nums[i]);
      }
    }

    if(nums.length != nonZeroArray.length){
       int rem=nums.length-nonZeroArray.length;
       for(int i=0; i<rem; i++){
           nonZeroArray.add(0);
       }
       // print(nonZeroArray);
     }
    // nums.clear();
    // nums=nonZeroArray;
    for(int i=0; i<nums.length; i++)
    {
       nums[i]=nonZeroArray[I];
    }
   }
  }

    3. Good programming practice with Inplace traversal -> don't try to use additional variables (like nonZeroArray her). Try to solve in nums itself in case of in place traversal,

    Alternative code:-

    class Solution {
   void moveZeroes(List<int> nums) {
   int listLenght = nums.length;
   nums.removeWhere((element) => element == 0);

   int listRemaningLenght = listLenght - nums.length;
   for (var i = 0; i < listRemaningLenght; i++) {
     nums.add(0);
   }
 }
}

    I hope this cleared your doubt.

    Thank you. Happy Coding.

    Regards:-

    Rakshath U Shetty