/*

* Author: klchang

* Date: 2017.12.16

* Description: Compute the number of 1 in the binary representation of an integer.

*/

#include <iostream>

#define INT_BITS 32

// Generic method: bitwise and operation with a number that has only one 1 in binary.

int numberOf_1_InBinary_Generic(int i)

{

    int count = ;

    int shiftCount = ;

    while (i && shiftCount < INT_BITS)

    {

        if (i & ) {

            ++ count;

        }

        i = i >> ;

        ++ shiftCount;

    }

    return count;

}

// Fast method: bitwise and operation between integer i and (i-1).

int numberOf_1_InBinary_Fast(int i)

{

    int count = ;

    while (i)

    {

        std::cout << "iter " << count << ": " << i << std::endl;

        i = i & (i - );

        count ++;

    }

    return count;

}

void unitest()

{

    int data[] = {-, , };

    std::cout << "---------------------- Generic Method -----------------------"  << std::endl;

    for (int i = ; i < ; ++i)

        std::cout << "The number of 1 in the binary representation of " << data[i] << " is "

                  << numberOf_1_InBinary_Generic(data[i]) << ".\n" << std::endl;

    std::cout << "----------------------- Fast Method --------------------------"  << std::endl;

    for (int i = ; i < ; ++i)

        std::cout << "The number of 1 in the binary representation of " << data[i] << " is "

                  << numberOf_1_InBinary_Fast(data[i]) << ".\n" << std::endl;

}

int main()

{

    unitest();

    return ;

}

#!/usr/bin/python

# -*- coding: utf8 -*-

"""

# Author: klchang

# Date: 2017.12.16

# Description: Compute the number of 1 in the binary representation of an integer.

"""

INT_BITS = 32

MAX_INT = (1 << (INT_BITS - 1)) - 1  # Maximum Integer for INT_BITS

# Generic method: bitwise and operation with a number that has only one 1 in binary.

def number_of_1_in_binary_generic(num):

    count, bit = 0, 1

    while num and bit <= MAX_INT + 1:

        if bit & num:

            count += 1

            num -= bit

        bit = bit << 1

    return count

# Fast method: bitwise and operation between integer num and (num-1).

def number_of_1_in_binary_fast(num):

    count = 0

    while num:

        if num < - MAX_INT - 1 or num > MAX_INT:

            break

        print("iter %d: %d" % (count, num))

        count += 1

        num = num & (num-1)

    return count

def unitest():

    nums = [-5, 0, 5]

    # Generic Method

    print("-" * 30 + " Generic Method " + "-" * 30)

    for n in nums:

        print("The number of 1 in the binary representation of %d is %d.\n" % (n, number_of_1_in_binary_generic(n)))

    # Fast Method

    print('\n' + "-" * 30 + " Fast Method " + "-" * 30)

    for n in nums:

        print("The number of 1 in the binary representation of %d is %d.\n" % (n, number_of_1_in_binary_fast(n)))

if __name__ == '__main__':

    unitest()

#pragma once

// The following macros define the minimum required platform.  The minimum required platform

// is the earliest version of Windows, Internet Explorer etc. that has the necessary features to run

// your application.  The macros work by enabling all features available on platform versions up to and

// including the version specified.

// Modify the following defines if you have to target a platform prior to the ones specified below.

// Refer to MSDN for the latest info on corresponding values for different platforms.

#ifndef _WIN32_WINNT            // Specifies that the minimum required platform is Windows Vista.

#define _WIN32_WINNT 0x0600     // Change this to the appropriate value to target other versions of Windows.

#endif

// stdafx.h : include file for standard system include files,

// or project specific include files that are used frequently, but

// are changed infrequently

//

#pragma once

#include "targetver.h"

#include <stdio.h>

#include <tchar.h>

// TODO: reference additional headers your program requires here

// stdafx.cpp : source file that includes just the standard includes

// NumberOf1.pch will be the pre-compiled header

// stdafx.obj will contain the pre-compiled type information

#include "stdafx.h"

// TODO: reference any additional headers you need in STDAFX.H

// and not in this file

// NumberOf1.cpp : Defines the entry point for the console application.

//

// 《剑指Offer——名企面试官精讲典型编程题》代码

// 著作权所有者：何海涛

#include "stdafx.h"

#include <string.h>

#include <stdlib.h>

// ====================方法一====================

int NumberOf1(unsigned int n);

int NumberOf1Between1AndN_Solution1(unsigned int n)

{

    int number = ;

    for(unsigned int i = ; i <= n; ++ i)

        number += NumberOf1(i);

    return number;

}

int NumberOf1(unsigned int n)

{

    int number = ;

    while(n)

    {

        if(n %  == )

            number ++;

        n = n / ;

    }

    return number;

}

// ====================方法二====================

int NumberOf1(const char* strN);

int PowerBase10(unsigned int n);

int NumberOf1Between1AndN_Solution2(int n)

{

    if(n <= )

        return ;

    char strN[];

    sprintf(strN, "%d", n);

    return NumberOf1(strN);

}

int NumberOf1(const char* strN)

{

    if(!strN || *strN < '' || *strN > '' || *strN == '\0')

        return ;

    int first = *strN - '';

    unsigned int length = static_cast<unsigned int>(strlen(strN));

    if(length ==  && first == )

        return ;

    if(length ==  && first > )

        return ;

    // 假设strN是"21345"

    // numFirstDigit是数字10000-19999的第一个位中1的数目

    int numFirstDigit = ;

    if(first > )

        numFirstDigit = PowerBase10(length - );

    else if(first == )

        numFirstDigit = atoi(strN + ) + ;

    // numOtherDigits是01346-21345除了第一位之外的数位中1的数目

    int numOtherDigits = first * (length - ) * PowerBase10(length - );

    // numRecursive是1-1345中1的数目

    int numRecursive = NumberOf1(strN + );

    return numFirstDigit + numOtherDigits + numRecursive;

}

int PowerBase10(unsigned int n)

{

    int result = ;

    for(unsigned int i = ; i < n; ++ i)

        result *= ;

    return result;

}

// ====================测试代码====================

void Test(char* testName, int n, int expected)

{

    if(testName != NULL)

        printf("%s begins: \n", testName);

    if(NumberOf1Between1AndN_Solution1(n) == expected)

        printf("Solution1 passed.\n");

    else

        printf("Solution1 failed.\n"); 

    if(NumberOf1Between1AndN_Solution2(n) == expected)

        printf("Solution2 passed.\n");

    else

        printf("Solution2 failed.\n"); 

    printf("\n");

}

void Test()

{

    Test("Test1", , );

    Test("Test2", , );

    Test("Test3", , );

    Test("Test4", , );

    Test("Test5", , );

    Test("Test6", , );

    Test("Test7", , );

    Test("Test8", , );

}

int _tmain(int argc, _TCHAR* argv[])

{

    Test();

    return ;

}