Need to generate random number in 2-D array

I am making a program where i have to generate 2-D array of N*N with random number without repetition such that one element is an alphabet .

Also if the matrix size is 3 then element must be between 1 and 8 without repetition and a single alphabet .

similarly for matrix of size 4 , element must be between 1 and 15 without repetition and a single alphabet .

Can anyone help ?

[code]

#include<stdio.h>
#include<conio.h>
#include<stdlib.h>
main()
{
int i,j,b,c,n ;

char ar[100][100];
char temp,ch;
printf("enter the size of the matrix : ");
scanf("%d",&n);


for(i=0;i<n;i++)
{
        printf("\n");
    for(j=0;j<n;j++)
    {

        scanf("%d",&ar[i][j]);
        printf("\t");


    }
}

ar[n-1][n-1] = 'E';

// for printing the array
    for(i=0;i<n;i++)

    {
        printf("\n");
    for(j=0;j<n;j++)

        {



            if(i==(n-1)&&j==(n-1))
        {
            printf("%c",ar[n-1][n-1]);
        }
            else
            printf("%d",ar[i][j]);

        printf("\t");



    }
}

printf("\n Press 'w' for shifting up 's' for down 'a' for left and     'd'       for right  : \n");

while(1)  //infinite loop
{

    for(i=0;i<n;i++)

    {

    for(j=0;j<n;j++)

        {

            if(ar[i][j]=='E')
            {
                b = i; //storing row
                c = j; // storing column
                printf("\t");
                ch = getch();

                switch(ch)

                {



                case 'w':




                if((i-1)>=0)
                {
                    system("CLS");
                    temp = ar[i-1][j];
                    ar[i-1][j] = ar[i][j];
                    ar[i][j] = temp;

                    for(i=0;i<n;i++)
                {
                        printf("\n");
                    for(j=0;j<n;j++)
                    {
                            if(i==(b-1)&&j==c)
        {
            printf("%c",ar[n-1][n-1]);
        }
            else
            printf("%d",ar[i][j]);

        printf("\t");

                    }
                }
                printf("\t");   
                }

                else
                {
                    printf("wrong move bro");
                }



                break;



                case 'a':




                if((j-1)>=0)
                {
                    system("CLS");
                    temp = ar[i][j-1];
                    ar[i][j-1] = ar[i][j];
                    ar[i][j] = temp;

                        for(i=0;i<n;i++)
                {
                    printf("\n");
                    for(j=0;j<n;j++)
                    {

                        if(i==b&&j==(c-1))
        {
            printf("%c",ar[n-1][n-1]);
        }
            else
            printf("%d",ar[i][j]);

        printf("\t");


                    }
                }
                printf("\t");   
                }

                else
                {


                printf("wrong move bro");
                }



                break;


                case 's' :

                if((i+1)<n)
                {
                    system("CLS");
                    temp = ar[i+1][j];
                    ar[i+1][j] = ar[i][j];
                    ar[i][j] = temp;

                        for(i=0;i<n;i++)
                {
                    printf("\n");
                    for(j=0;j<n;j++)
                    {

                        if(i==(b+1)&&j==c)
        {
            printf("%c",ar[n-1][n-1]);
        }
            else
            printf("%d",ar[i][j]);

        printf("\t");


                    }
                }
                printf("\t");   
                }

                else
                {


                printf("wrong move bro");
                }
                break;

                case 'd' :

                    if((j+1)<n)
                {
                    system("CLS");
                    temp = ar[i][j+1];
                    ar[i][j+1] = ar[i][j];
                    ar[i][j] = temp;

                        for(i=0;i<n;i++)
                {
                    printf("\n");
                    for(j=0;j<n;j++)
                    {

                        if(i==b&&j==(c+1))
        {
            printf("%c",ar[n-1][n-1]);
        }
            else
            printf("%d",ar[i][j]);

        printf("\t");


                    }
                }
                printf("\t");   
                }

                else
                {


                printf("\n wrong move bro");

                }
                break;










            }  //switch end





        }  //if end



























}  //for end

} //for end

} //while end

} // main end

[/code]