CareerCup-5.3

Given an integer, print the next smallest and next largest number that have the sam number of 1 bits in their binary representation.

理解题意费了些时间。明白了之后就没什么难度了。答案没考虑负数的情况和无法找到这样的数字的情况，同时有一定的冗余。

#include <iostream>
#include <bitset>
using namespace std;
#define MAX_INDEX 30

bool getBit(int data, int i)
{
    return (data & (1 << i)) >> i;
};

int setBit(int data, int i, bool v)
{
    if(v)
    {
        return (data | (1 << i));
    } else {
        return (data & ~(1 << i));
    }
};

int getNext(int d, bool isLarger)
{
    int index = 0;
    while(isLarger^getBit(d, index) && index <= MAX_INDEX)
    {
        index++;
    };
    while(!isLarger^getBit(d, index) && index <= MAX_INDEX)
    {
        index++;
    }
    if(index > MAX_INDEX)
    {
        cout<<"Can not find"<<endl;
        return 0;
    }
    d = setBit(d, index--, isLarger);
    d = setBit(d, index--, !isLarger);
    int i=0;
    while(index > i)
    {
        while(isLarger^getBit(d, index))
        {
            index--;
        }
        while(!isLarger^getBit(d, i))
        {
            i++;
        }
        if(index > i)
        {
            d = setBit(d, index, !isLarger);
            d = setBit(d, i, isLarger);
        }
    }
    return d;
};

int getNextLarger(int d)
{
    if(d >= 0)
        return getNext(d, true);
    else
        return -getNext(-d, false);
};

int getNextSmaller(int d)
{
    if(d >= 0)
        return getNext(d, false);
    else
        return -getNext(-d, true);
};

int main()
{
    cout<<getNextLarger(4)<<endl<<getNextSmaller(4)<<endl;
    cout<<getNextLarger(-4)<<endl<<getNextSmaller(-4)<<endl;
    system("pause"); 
};