01-complexity 3 binary search, 01-Binary Search

01-complexity 3 binary search, 01-Binary Search

This is a function question. The question provides corresponding interfaces to complete the subfunction. The given function interfaces and struct are defined as follows:

#include <stdio.h>
#include <stdlib.h>

#define MAXSIZE 10
#define NotFound 0
Typedef int ElementType;

Typedef int Position;
Typedef struct LNode *List;
Struct LNode {
     ElementType Data[MAXSIZE];
     Position Last; /* Saves the position of the last element in the linear table */
};

List ReadInput(); /* Referee implementation, details are not listed. The element is stored starting from subscript 1 */
Position BinarySearch( List L, ElementType X );

Int main()
{
     List L;
     ElementType X;
     Position P;

     L = ReadInput();
     Scanf("%d", &X);
     P = BinarySearch( L, X );
     Printf("%d\n", P);

     Return 0;
}

/* Your code will be embedded here */

We can see that we need to perform binary search for a linear table stored in a linked list. The procedure is as follows:

Position BinarySearch( List L, ElementType X )
{
    Position mid;
    Position low = 1;
    Position high = L->Last;
    while(low <= high) {
        mid = low + (high - low)/2;
        if(X < L->Data[mid]) 
            high = mid - 1;
        else if (X > L->Data[mid]) 
            low = mid + 1;
        else 
            return mid;
    }
    return NotFound ;    
} 

Note that the while LOOP condition must be Left <= Right. Otherwise, when the two indicate the same number, "NotFound" is directly considered if the condition does not enter the loop judgment, resulting in incorrect results.