import'dart:collection'; classSolution { List<int> addToArrayForm(List<int> num, int k) { Queue<int> res =Queue(); int carry =0; int i =0; /* We always start computing from array's last element and k's last digit and will compute sum and carry. We will iterate it till k and index of array both have existence. If one of them gets exhausted the for loop below will not work. */for (i =num.length -1; i >=0&& k >0; i--) { int temp =num[i]; res.addFirst((temp + carry + (k %10)) %10); carry = (temp + carry + (k %10)) ~/10; k ~/=10; } /* If for an instance your k is greater than the number that is present in the form of array then the below while loop will work. */while (k !=0) { int compute = (k %10) + carry; res.addFirst(compute %10); carry = compute ~/10; k ~/=10; } /* If for an instance the number that is present in the form of array is greater than k then the below for loop will work. */for (int r = i; r >=0; r--) { int temp =num[r]; res.addFirst((temp + carry) %10); carry = (temp + carry) ~/10; } /* If there is some carry still remaining at last then add it to beginning of the array-list or Queue. */if (carry !=0) res.addFirst(carry); return res.toList(); } }We are taking k as carry. We start from the last or lowest digit in array num add k. Then update k and move until the highest digit. After traversing array if carry is > 0 then we add it to beginning of num.
Example: num = [2,1,5], k = 806 At index 2 num = [2, 1, 811] So, k = 81 and num = [2, 1, 1]
At index 1 num = [2, 82, 1] So, k = 8 and num = [2, 2, 1]
At index 0 num = [10, 2, 1] So, k = 1 and num = [0, 2, 1]
Now k > 0 So, we add at the beginning of num num = [1, 0, 2, 1]
classSolution { List<int> addToArrayForm(List<int> num, int k) { Queue<int> res =Queue(); int len =num.length -1; while (len >=0|| k >0) { if (len >=0) { k +=num[len--]; } res.addFirst(k %10); k ~/=10; } return res.toList(); } }