AKHIL AND COLORED BALLS

• Problem Description

  
  "Akhil has many balls of white and black colors. One day, he was playing with them. During the play, he arranged the balls into two rows both consisting of N number of balls. These two rows of balls are given to you in the form of strings X, Y. Both these string consist of W and B, where W denotes a white colored ball and B a black colored.
  
  Other than these two rows of balls, Akhil has an infinite supply of extra balls of each color. he wants to create another row of N balls, Z in such a way that the sum of hamming distance between X and Z, and hamming distance between Y and Z is maximized.
  
  Hamming Distance between two strings X and Y is defined as the number of positions where the color of balls in row X differs from the row Y ball at that position. e.g. hamming distance between ""WBB"", ""BWB"" is 2, as at position 1 and 2, corresponding colors in the two strings differ.
  .
  
  As there can be multiple such arrangements of row Z, Akhil wants you to find the lexicographically smallest arrangement which will maximize the above value.
  Input
  
  The first line of the input contains an integer T denoting the number of test cases. The description of T test cases follows:
  First line of each test case will contain a string X denoting the arrangement of balls in first row
  Second line will contain the string Y denoting the arrangement of balls in second row.
  
  Output
  
  For each test case, output a single line containing the string of length N denoting the arrangement of colors of the balls belonging to row Z.
  
  Constraints
  
  1 <=T<= 3
  
  Subtasks
  Subtask #1 (10 points) : 1<= N <=16
  Subtask #2 (20 points) : 1<= N <=103
  Subtask #3 (70 points) : 1<= N <=105
  Example
  
  Input:
  1
  WBWB
  WBBB
  
  Output:
  BWBW
  
  Explanation
  
  Example case 1. As we know, Hamming Distance(WBWB, BWBW) + Hamming Distance(WBBB, BWBW) = 4 + 3 = 7.
  You can try any other value for string Z, it will never exceed 6. "
  

• CODING ARENA

• #include <stdio.h>

  int main()

  {

    int t,i;

    char a[100003],b[100004];

    scanf("%d",&t);

    while(t--)

    {

      scanf("%s",a);

      scanf("%s",b);

      i=0;

      while(a[i]!='\0')

      {

        if(a[i]=='W' && b[i]=='W')

          printf("B");

        else if(a[i]=='B' && b[i]=='B')

          printf("W");

        else

          printf("B");

        i++;

      }

      printf("\n");

    }

  return 0;

  }

• Test Case 1

  
  Input (stdin)

  1
  
  WBWB
  
  WBBB
  
  

  Expected Output

  BWBW

• Test Case 2

  
  Input (stdin)

  1
  
  WBBB
  
  WBBB
  
  

  Expected Output

  BWWW