How to implement bubble sort in C.

Question

I am trying to implement the bubble sort algorithm in C. Here is what I have so far:

#include<stdio.h>
void bubble_sort(int m, int a[100000]);
void main()
{
int a[100000], i, m;
FILE * be;

be=fopen("be.txt","r");
for (i=0; !(feof(be)); ++i)
    fscanf(be,"%i", a+i);
m=i-1;
bubble_sort(m ,a);
fclose(be);
}
void bubble_sort(int m, int a[100000])
{
int i, ok, v, n=m;;
for (;!ok;ok=1)
{
    ok=0;
    for (i=0;i<=m-1;++i)
    {
        if (*(a+i)>*(a+i+1)) { v=*(a+i); *(a+i)=*(a+i+1); *(a+i+1)=v; ok=0;}
    }
    m=m-1;
}

for (i=0; i<n; ++i)
    printf("%i ", a[i]);
}

My pseudo code:

Bubblesort2( A )
m:=length( A ) - 1
repeat
    OK := true
    for i := 0 to m-1 do
        if Ai > Ai+1 then
            Ai <=>Ai+1
            OK := false
    m := m - 1
until OK

This doesn't work right. What is the code to implement he bubble sort in C?

Answer 1

Try this:

void bubble_sort(int m, int a[100000])
{
    int i, ok = 0, v, n = m;
    while ( !ok )
    {
        ok = 1;
        for ( i=0; i < m-1; ++i )
        {
            if ( *(a+i) > *(a+i+1) ) 
            { 
                v = *(a+i); 
                *(a+i) = *(a+i+1); 
                *(a+i+1) = v; 
                ok = 0;
            }
        }

        m--;
    }

    for ( i = 0; i < n; ++i )
        printf("%i ", a[i]);
}

Basically, initialize ok (local variables are initialized with garbage values). You also must set ok = 1 when entering the loop and ok = 0 if a swap took place. There's no point in using a for loop, a while loop is more readable. m = m - 1 can be replaced with m--, it's the same thing and you write less code.