MOOC 实现二分查找算法（基于顺序表）

 1 #include <stdio.h>
 2 #include <stdlib.h>
 3 #define MAXSIZE 10
 4 #define NotFound 0
 5 typedef int ElementType;
 6 typedef int Position;
 7 typedef struct LNode *List;
 8 struct LNode {
 9     ElementType Data[MAXSIZE];
10     Position Last; /* 保存线性表中最后一个元素的位置 */
11 };
12 List ReadInput(); /* 裁判实现，细节不表。元素从下标1开始存储 */
13 Position BinarySearch( List L, ElementType X );
14 int main()
15 {
16     List L;
17     ElementType X;
18     Position P;
19     L = ReadInput();
20     scanf("%d", &X);
21     P = BinarySearch( L, X );
22     printf("%d\n", P);
23     return 0;
24 }
25 
26 /* 你的代码将被嵌在这里 */
27 List ReadInput(){
28     List PtrL;
29       int N;
30       scanf("%d", &N);
31       for(int i = 1; i <= N; i++){
32         scanf("%d",&PtrL->Data[i]);
33       }
34       PtrL->Last = N;
35       return PtrL;
36 }
37 Position BinarySearch( List L, ElementType X ){
38     int Left = 1, Right = L->Last, mid;
39     while(Right - Left >= 0 ){
40         mid = (Left + Right) / 2;
41         if(L->Data[mid] > X){
42             Right = mid - 1;
43         }else if(L->Data[mid] == X){
44             return mid;
45         }else{
46             Left = mid + 1;
47         }
48     }
49     return NotFound;
50 }