C++ error: Array subscript is not an integer

Question

I am writing this partition code and there seems to be some problems with my RandomInRange function

Does anyone know how to write this Swap function? Ok,so I got the first few bugs fixed, the last problem is (I think) with my Swap() function.

#include <iostream>
#include <cstdio>
#include <stdlib.h>
#include <exception>
using namespace std;

int RandomInRange(int start,int end)
{
    return (rand()%(end-start+1)+start);
}

void Swap(int* a,int* b)
{
    int* temp=a;
    a=b;
    b=temp;
    return;
}


int Partition(int data[],int length,int start,int end)
{
    if(data==NULL || length<=0 || start<0 || end>=length)
    {//throw new exception("Invalid Parameters.");

    }

    int index=RandomInRange(start,end);
    Swap(&data[index],&data[end]);

    int small = start-1;
    for(index = start; index < end; ++index)
    {
        if(data[index]<data[end])
        {
            ++small;
            if(small!=index)
                Swap(&data[index],&data[small]);
        }

    }
    ++small;
    if(small != index)
        Swap(&data[index],&data[small]);

    return small;

}


int main(void)
{
    int a[]={9,0,-4,23,5,21,3,-1};
    Partition(a,8,1,8);
    for(int i=0;i<8;i++)
        cout<<a[i];
    return 0;
}

//results={9,0,-4,23,5,21,3,-1}, so it's not actually sorted..

And emm,just a tiny question. Has anyone read the STL source code? Does it help to learn C++ and data structure? I was hoping to achive higher grades for my finals.

Also it says:

No matching constructor for initialization of 'std::exception'

when I try the code:

throw new exception("Invalid Parameters.");

That's why I commented that line.

Answer 1

In the below code

int Partition(int data[],int length,int start,int end)
{
    if(data==NULL || length<=0 || start<0 || end>=length)
        //throw new exception("Invalid Parameters.");

    int index=RandomInRange(start,end);
    Swap(&data[index],&data[end]);

after

if(data==NULL || length<=0 || start<0 || end>=length)

you have commented throwing the exception. Hence the program control moves to the next statement which calls the method RandomInRange() whose arguments start and end are invalid. Hence this error.