Radix sort using counting sort

Question

This radix sort algorithm is using counting sort as the stable sort required in it. This sorts correctly when given an input of 3 numbers with small number of digits but the sorting algorithm stops working for higher input values. Thanks in advance

   #include<stdio.h>
    int digits(int k)
    {
        int i=0;
        while(k!=0)
        {
            k=k/10;
            i++;
        }
        return i;
    }
    void radixsort(int a[],int size,int k)
    {
        int c[10],b[50],i,j,l,m=10,n=1;
        for(l=1;l<=k;l++)
        {
            if(l==1)
            {
                m=10;
                n=1;
            }
            else
            {
                m=m*10;
                n=n*10;
            }
            for(i=0;i<=9;i++)
            {
                c[i]=0;
            }
            for(j=1;j<=size;j++)
            {
                c[(a[j]%m)/n]=c[(a[j]%m)/n]+1;
            }
            for(i=0;i<=9;i++)
            {
                c[i]=c[i-1]+c[i];
            }
            for(j=size;j>=1;j--)
            {
                b[c[(a[j]%m)/n]]=a[j];
                c[(a[j]%m)/n]--;
            }
            for(i=1;i<=size;i++)
            {
                a[i]=b[i];
            }
        }
    }
    main()
    {
        int a[50],i,size,k=0;
        printf("enter the size of the array\n");
        scanf("%d",&size);
        printf("enter the numbers of the elements\n");
        for(i=1;i<=size;i++)
        {
            scanf("%d",&a[i]);
            if(k<a[i])
            k=a[i];
        }
        radixsort(a,size,k);
        for(i=1;i<=size;i++)
        {
            printf("%d\n",a[i]);
        }
    }

Answer 1

The move part of the loop is moving from the end of array to start, this will not be stable. The digits function is never called. for(j=1; ... ) should be for(j = 0; j < size; ... The next loop is using c[i-1] when i is zero. You could use int c[11] instead of c[10], and use c[1+(a[ ...] ...] ++, then ignore c[10] when converting counts into indices (c[0] = 0, c[1] = #0's, c[2] = #0's + #1's, ...), then move from start to end (j=0; j < size; ...) . – rcgldr