Can a MongoDB key have two arrays?

Why is my solution for adding two binary arrays not working?

• Following is the problem from CLRS book Consider the problem of adding two n-bit binary integers, stored in two n-element arrays A and B. The sum of the two integers should be stored in binary form in an (n +1)element array C. State the problem formally and write pseudocode for adding the two integers. I found the pseudocode as Adding-A-B(A, B, C) key ← 0 for i ← 1 to n do sum ← A[i] + B[i] + key C[i] ← sum mod 2 key ← sum div 2 C[n + 1] ← key Here is my code public static void main(String[] args) { int[] a = {1,1,1,1}; int[] b = {1,0,1,0}; int[] c = new int[a.length+1]; StringBuffer sb1 = new StringBuffer(); StringBuffer sb2 = new StringBuffer(); int key = 0; for (int i = 0; i < a.length; i++) { c[i] = (a[i] + b[i] + key) % 2; key = (a[i] + b[i] + key) / 2; } c[a.length] = key; for (int j = 0; j < c.length; j++) System.out.println(c[j]); } Expected output = 11001 Actual output = 00101. 1)  May I know where I am making mistake 2) How does module by 2 and div by 2 for key works?

• Answer:

  Did you try to debug it? Edit: Aha!! Your program works perfectly. It;s a feature, not a bug. Probably the problem is that you didn;t realize how arrays work. Since, your least significant integer is at position 0, what you are doing is 0101 + 1111 , not 1010+1111. 0101+1111  = 10100, not 11001. Since you are printing the least significant integer is being printed first, you are printing 10100 as 00101. Debug through the code and you might see the problem.  If you want it to work as you expect, you should reverse your for loop