Marathon Runner

Bob was conducting a marathon for World Exercise day. The marathon was n kilo meters long. Bob wanted to place refreshments at P points within the race. The supply was given at mile marker 0. Each of the P places had a van each. Each van would travel only till the next refreshment point. Find out of all the vans which van travelled the most.

Input

The first line contains an integer T. The number of test cases.
For each test case the first line contains two integers N, P. N - the total distance of the marathons and P - the number of refreshment spots.
In the next line P  integers are given, the locations of all the refreshment spots.

Output

The most distance travelled by any van. Print the answer for each test case in a separate line.

Constraints:

1<=T<=100

2<=N<=1000

1<=P<=200

0 <P_i< N,  where P_i is the mile marker of each refreshment spots.
It is guaranteed that each mile marker will contain only one refreshment spot.

Sample Input

2

7 3

6 2 4

11 2

6 2

Sample Output

2

5

Explanation:

In the first test case the first 3 vans travel for a distance 2 kms (0-2, 2-4,4-6) and the last one a distance of 1 km (6-7).
In the second test case the the vans travel 2, 4 and 5 kms respectively. (0-2, 2-6,6-11)

Program:

#include<stdio.h>
void sort(int *,int);                                             /* function prototype           */
int main()
{
              int n,p,temp,diff=0,i,j,k,test_cases;
              printf("input the number of test cases");
              scanf("%d",&test_cases);
              if((test_cases<1)||(test_cases>100))
              printf("Invalid range");
              else
             {
                      for(k=1;k<=test_cases;k++)
                     {
                              printf("input the marathon long in km");
                              scanf("%d",&n);
                              if((n<2)||(n>1000))
                              printf("please give the valid length");
                              else{
                                       printf("enter number of refreshment points");
                                       scanf("%d",&p);
                                       if(((p<1)||(p>n))||(p>200))
                                       printf("enter the valid number of refreshment points\n");

                                       else
                                       {
                                                   int refresh_points[p+1];
                                                   refresh_points[0]=0;
                                                   refresh_points[p+1]=n;
                                                   printf("enter the locations of refreshment points");
                                                   for(i=1;i<=p;i++)
                                                   scanf("%d",&refresh_points[i]);
                                                   sort(refresh_points,p);
                                                   for(i=1;i<=p;i++)
                                                   {
                                                          temp=refresh_points[i+1]-refresh_points[i];
                                                          if(temp>diff)
                                                          diff=temp;
                                                    }
                                                    printf("%d\n",diff);
                                        }
                                     }
                       }
              }
              return 0;
}
void sort(int *refresh_points,int p )
{
           int temp,i,j;
           for(i=1;i<=p;i++)
                  for(j=i+1;j<=p;j++)
                       if((*(refresh_points+i))>(*(refresh_points+j)))
                       {
                               temp=*(refresh_points+i);
                              (*(refresh_points+i))=(*(refresh_points+j));
                              *(refresh_points+j)=temp;
                       } 
}