Efficient java program to find GCD of given two numbers

The following java code finds the biggest common factor(GCD) for two numbers easily. Otherwise we need to check it from smallest number.Lets assume that the smallest number is n. So we need to check it from n,n-1....1 to find the common factor.But here out of two inputs set the biggest one to b. Then find the common factor using the % operator and keep changing the values of a and b until you find the common factor.

Code : (in JAVA)

 Sample input and output
1.Input
   8 5
  Output
   1
2.Input 
   26 4
  Output
   2

Please let me know if you have any questions .

Simple C Program to reverse Singly LinkedList using recursion

Code:

void reverse(struct node** headRef) 
{
     struct node* first;
     struct node* rest;
     if (*headRef == NULL) 
            return;
     first = *headRef;
     rest = first->next;
     if (rest == NULL) return;
     reverse(&rest);
     first->next->next = first;
     first->next = NULL;
    *headRef = rest;
  }

Simple C Code to Create Magic matrix

First we have to understand what is magic matrix.

•   In magic matrix every rows and column sums are equal.
•   Diagonal sum is also equal.
•   The following code has O(n^2) time complexity.
•   The example for magic matrix is given below.

               8     1       6
                               
               3      5      7        //rows,column,diagonal sum are equal
                      
               4      9      2       //here n is 3


Here is the code
 
   void magic_matrix(int n)          // N should be odd number...
   {   int i,j,k,num=1;            
        i=1;
        j=(1+n)/2;
        for(k=0;k < n*n;k++)  
        { a[i-1][j-1]=num;num++;
           i--;
           j++;
           if(i==0) i=n;
           if(j==n+1) j=1;
           if(a[i-1][j-1]!=0)
          { i+=2;
            j--;
            if(i>n) i=i-n;
            if(j==0) j=n;
           }
         }
    for(i=0;i < n;i++)
    {for(j=0;j < n;j++)
      { printf("%d\t",a[i][j]);
       }
      printf("\n");              
       }
 }