Question

i am trying to implement the insertion sort algorithm using Obj-c i converted the commented lines below from C into Obj C , (hope they are correct if anybody can have a look and assist) but the application crashes with the following error Terminating app due to uncaught exception ‘NSRangeException’, reason: ‘* -[NSMutableArray objectAtIndex:]: index 4294967295 beyond bounds [0 .. 9]’

-(IBAction)clicked_insertsort:(id)sender{

    NSMutableArray  *iarray = [[NSMutableArray alloc]initWithArray:garr];
    int n = [iarray count]  ;
    NSLog(@"%@",iarray);

    int i,j,x,k;

     for(i=1;i<=n-1;i++)  

     {  
     j=i;  

     //x=a[i]; 
    x=[[iarray objectAtIndex:(NSUInteger)i]intValue];    

     //while(a[j-1]>x && j>0)  
     while ([[iarray objectAtIndex:(NSUInteger)j-1]intValue] >x && j>0)


     {  

     //a[j]=a[j-1];
    [iarray replaceObjectAtIndex: (j) withObject: [iarray objectAtIndex: (j-1)]];
     j=j-1;  
     }  

    // a[j]=x;  
    [[iarray objectAtIndex:(NSUInteger)j]intValue] == x; 

     }
    NSLog(@"%@",iarray);
}

Answer 1

You should avoid casting your indexes to unsigned int. try it one at a time and which ever one changes the error to say -1 rather than 4294967295 is the index you are having a problem with

When j gets set to 0 you’re now going to be indexing into iarray at index -1, which when casted to an unsigned int is equal to 4294967295