Bubble sort not working properly

Question

do
{
    swap=false;
    for(int i=0; i<256; i++)
    {
    if(pd[i]<pd[i+1])
    {
        int temp=pd[i];
            pd[i]=pd[i+1];
            pd[i+1]=temp;
        swap=true;
        }
    }
}
while(swap);

It only returns top two results properly and the rest as 0. I am sorting floats.

You mean, you are comparing floating points using `<` operator? .. you need to use epsilon. Check this - http://stackoverflow.com/questions/10334688/how-dangerous-is-it-to-compare-floating-point-values — Sangeeth Saravanaraj, Apr 26 '12 at 14:23
@SangeethSaravanaraj: you only need epsilon values when doing equality checks. This is relational so it won't be a problem. — Skizz, Apr 26 '12 at 14:24

score 9 · Accepted Answer · answered Apr 26 '12 at 14:22

9

I am sorting floats.

In this case, temp must be of type float:

float temp=pd[i];

Otherwise, you're truncating pd[i] to int each time you do a swap.

Also, if your float array might contain NaNs, they'll require extra care in comparisons.

answered Apr 26 '12 at 14:22

NPE

486,780
108
951
1,012

How stupid was i? , just forgot temp declare temp as float . – Alex David Apr 26 '12 at 14:24
@aix can we compare floating points using `>` or `<` operators?! – Sangeeth Saravanaraj Apr 26 '12 at 14:24
@SangeethSaravanaraj: For sorting purposes, yes. Except for NaNs (they have somewhat tricky comparison semantics). – NPE Apr 26 '12 at 14:25
Yes you can compare float using '<' '>' operators. – Alex David Apr 26 '12 at 14:26
+1, I would +2 if I could because you mention dealing with `NaN`, which people forget too often. – Romain Apr 26 '12 at 14:28

score 1 · Answer 2 · answered Apr 26 '12 at 14:25

1

temp is of type int, but your array is of type float...

answered Apr 26 '12 at 14:25

md5

23,373
3
44
93

yes i got it, but thanks for the help anyway. – Alex David Apr 26 '12 at 14:27

Bubble sort not working properly

2 Answers2