获取1的总数源代码

// CountOnes.cpp : Defines the entry point for the console application.
//
#include "stdafx.h"
#include <iostream>
using namespace std;
int GetOneCount(int nNum);
int GetOneCountEx(int nNum);
int main()
{
	int i = 0;
	/*for (i = 0; i < 0xffff; i++)
	{
		cout << "i = " << i << "  1s = " << GetOneCount(i) << endl;
	}*/
	cout << "i = " << 0xffff - 1<< "  1s = " << GetOneCountEx(0xffff - 1) << endl;
	return 0;
}
int GetOneCount(int nNum)
{
	int i		= 0;
	int nCount	= 0;
	int nTemp	= 0;
	for (i = 0; i < nNum; i++)
	{
		nTemp = i;
		while (nTemp)
		{
			if (1 == nTemp % 10)
			{
				nCount++;
			}
			nTemp /= 10;
		}
	}	
	return nCount;
}
int GetOneCountEx(int nNum)
{
	int nCount		= 0;
	int nFac		= 1;
	int nLowNum		= 0;
	int nHiNum		= 0;
	int nCurrNum	= 0;
	while (nNum / nFac)
	{
		nLowNum = nNum - (nNum / nFac) * nFac;
		nHiNum = nNum / (nFac * 10);
		nCurrNum = (nNum / nFac) % 10;
		int nTemp = nCount;
		switch (nCurrNum)
		{
		case 0:
			nCount += nHiNum * nFac;
			break;
		case 1:
			nCount += nHiNum * nFac + nLowNum + 1;
			break;
		default:
			nCount += (nHiNum + 1) * nFac;
			break;
		}
		cout << "nCount = " << nCount << "\tnCurrCount = " << nCount - nTemp << "\tnLowNum = " << nLowNum << "\tnHiNum = " << nHiNum << "\tnCurrNum = " << nCurrNum << endl;
		nFac *= 10;
	}
	return nCount;
}