Bitwise Operation Explained

1.统计一个数置位为1的个数

#include <stdio.h>
int __numOf_SET_Bits(int var)
{
    if (var==0) return 0;
    else return (var&01)?1+__numOf_SET_Bits(var>>1):__numOf_SET_Bits(var>>1);
}
int main()
{
    int var=128;
    printf("Num of Bits: %d\n",__numOf_SET_Bits(var));
    return 0;
}

2,判断一个数是奇数还是偶数

#include <stdio.h>
#define isEven(a) ((((a)&01)==0)?1:0)
int main()
{
    int var=1;
    if(isEven(var))
    {
        printf("%d is a even number \n",var);
    }
    else
        printf("%d is a odd number \n",var);
    return 0;
}

方法二：

#include <stdio.h>
#define isEven(a) ((((a)%2)==0)?1:0)
int main()
{
    int var=11;
    if(isEven(var))
    {
        printf("%d is a even number \n",var);
    }
    else
        printf("%d is a odd number \n",var);
    return 0;
}

3，判断一个数是否是2的幂次方

#include <stdio.h>
#define __isPower_of_TWO(a) (((a)&(a-1))==0)?1:0
int main()
{
    int arr[] = {1,2,3,4,5,8,9,16};
    int i=0;
    for(;i<sizeof(arr)/sizeof(arr[0]);i++)
    {
        if (__isPower_of_TWO(*(arr+i)))
            printf("%d has a form of Power of Two \n",*(arr+i));
        else
            printf("%d is not in the form \n", *(arr+i));
    }
    return 0;
}

方法二：

#include <stdio.h>
#define __isPower_of_TWO(a) (((a)&(-a))==a)?1:0
int main()
{
    int arr[] = {1,2,3,4,5,8,9,16};
    int i=0;
    for(;i<sizeof(arr)/sizeof(arr[0]);i++)
    {
        if (__isPower_of_TWO(*(arr+i)))
            printf("%d has a form of Power of Two \n",*(arr+i));
        else
            printf("%d is not in the form \n", *(arr+i));
    }
    return 0;
}

方法三：

#include <stdio.h>
#include <stdlib.h>
int __numOf_SET_Bits(int var)
{
    if (var==0) return 0;
    else return (var&01)?1+__numOf_SET_Bits(var>>1):__numOf_SET_Bits(var>>1);
}

int main()
{
    int arr[] = {1,2,3,4,5,8,9,16};
    int i=0;
    for(;i<sizeof(arr)/sizeof(arr[0]);i++)
    {
        if (__numOf_SET_Bits(arr[i])==1)
            printf("%d has a form of Power of Two \n",*(arr+i));
        else
            printf("%d is not in the form \n", *(arr+i));
    }
    system("pause");
    return 0;
}

4，不使用第三个数，交换两个数

#include <stdio.h>
void __SWAP(int *a,int *b)
{
    *a = *a ^ *b;
    *b = *a ^ *b;
    *a = *a ^ *b;
}
int main()
{
    int a=5, b=6;
    printf("Before swap: a=%d <=====> b=%d \n",a,b);
    __SWAP(&a,&b);
    printf("After  swap: a=%d <=====> b=%d \n",a,b);
    return 0;
}

5，异或双向链表

#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
typedef struct XOR_based_Node
{
    int data;//数据域
    unsigned long compressedAddress;
}node;
node* head = NULL;//异或双向链表表头
void add_element_to_list(node** headRef, int data)
{//插入表头
    node *newNode = (node*)malloc(sizeof(node));
    assert(newNode);
    newNode->compressedAddress = (unsigned long)(*headRef);
    newNode->data = data;
    if(*headRef != NULL)
        (*headRef)->compressedAddress ^= (unsigned long)newNode;
    *headRef=newNode;
}
void printList(node* head)
{//输出表
    unsigned long prev = 0;
    while(head)
    {
        unsigned long next = prev ^ head->compressedAddress;
        printf("%d ", head->data);
        prev = (unsigned long)head;
        head = (node *)next;
    }
    printf("\n");
}
int main(void)
{
    int i=0;
    for(;i<10;i++)
        add_element_to_list(&head,i);
    printList(head);
    return 0;
}