改进的二分查找

//改进的二分查找

//如果待查找的数组中存在相同元素，则返回相同元素第一个的下标

/*

递归算法

int searchB1(int A[], int low, int high, int data);

非递归算法

int searchB2(int A[], int len, int data);

*/

#include<stdio.h>

#include<string.h>

#define Len 25

//递归算法

int searchB1(int A[], int low, int high, int data);

//非递归算法

int searchB2(int A[], int len, int data);

void main()

{

int i;

int len = 0;

int data; //要查找的字符

int result = 0;

int A[] = {1,3,3,3,3,6,7,8,9};

len = sizeof(A) / sizeof(int);

printf("output the primary data:");

for(i = 0; i < len; i++)

{

if( i % 5 == 0)

printf("\n");

printf("A[%d]:%d\t",i,A[i]);

}

printf("\nintput the searched char:");

scanf("%d",&data);

result = searchB1(A,0,len-1,data);

printf("recursion search.\n");

if( result == -1 )

{

printf("Sorry,no this char.\n");

}

else

{

printf("the char is %d.\n",A[result]);

printf("the index of the char in Array is %d.\n",result);

}

result = searchB2(A,len,data);

printf("unrecursion search.\n");

if( result == -1 )

{

printf("Sorry,no this char.\n");

}

else

{

printf("the char is %d.\n",A[result]);

printf("the index of the char in Array is %d.\n",result);

}

}

//非递归算法

int searchB2(int A[], int len, int data)

{

int low = 0;

int high = len - 1;

int mid = 0;

while( low <= high )

{

mid = ( low + high ) / 2;

if( A[mid] == data )

{

if(low == high )

return mid;

else

{

if( A[mid - 1] == data )

{//A[mid]和A[mid-1]都等于data,则继续查找

high = mid - 1;

}

else

{

return mid;

}

}

}

else if( A[mid] < data )

{

low = mid + 1;

}

else

{

high = mid - 1;

}

}//end while

//没有返回-1

return -1;

}

int searchB1(int A[], int low, int high, int data)

{

if( low <= high )

{

int mid = ( low + high ) / 2; //low+((high-low)/2)可能更严谨

if( A[mid] == data )

{

if(low == high )

return mid;

else

{

if( A[mid - 1] == data )

{//A[mid]和A[mid-1]都等于data,则继续查找

high = mid - 1;

return searchB1(A,low,high,data);

}

else

{

return mid;

}

}

}

else if( A[mid] < data )

{

low = mid + 1;

return searchB1(A,low,high,data);

}

else

{

high = mid - 1;

return searchB1(A,low,high,data);

}

}

else

{ //没有返回-1

return -1;

}

}



/*博主寄语：如若发现错误，望指出，谢谢*/