Average two numbers

// average.cpp : Defines the entry point for the console application .
//

#include "stdafx.h"

// There is Bug edition : Integer overflow
unsigned average1(unsigned a, unsigned b)
{
    return (a + b) / 2;
}

// The following is the correct version ：
unsigned average2(unsigned low, unsigned high)
{
    return low + (high - low) / 2;
}

unsigned average3(unsigned a, unsigned b)
{
    return (a / 2) + (b / 2) + (a & b & 1);
}

unsigned average4(unsigned a, unsigned b)
{
    return (a & b) + (a ^ b) / 2;
}

int _tmain(int argc, _TCHAR* argv[])
{
    int a = 10;
    int b = 7;

    unsigned int result = average4(0x80000000U, 0x80000000U);
    printf("%d", result);

    return 0;
}

On finding the average of two unsigned integers without overflow - The Old New Thing (microsoft.com)