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函数应用3

上一篇 / 下一篇 2011-03-14 20:43:50

 Filename:  binary.c  *    Description: 从一组排序好的序列里找出某个元素的位置（折半查找）  
 * ========================================================================== 
 */
#include <stdio.h> 
#define LEN 8 
  
int a[LEN] = { 1, 2, 2, 5, 5, 6, 8, 9 }; 
  
int binary(int number) 
{ 
    int mid, start = 0, end = LEN - 1; 
  
    while (start <= end) { 
        mid = (start + end) / 2; 
        if (a[mid] < number) 
            start = mid + 1; 
        else if (a[mid] > number) 
            end = mid - 1; 
        else { 
            while (a[mid] == number) { 
                --mid; 
            };  //返回最早出现的匹配位值 
            return mid + 1; 
        } 
    } 
    return -1; 
} 
  
int main(void) 
{ 
    printf("%d\n", binary(2)); 
    return 0; 
}