# 【二分查找法（折半查找法）】

/*二分查找法

[3 24 57 57 67 68 83 90 92 95]

3 24 57 57 67 [68 83 90 92 95]

3 24 57 57 67 68 83 90 [92 95]
*/

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

#define MAX 10
#define SWAP(x,y) {int t; t = x; x = y; y = t;}

void quicksort(int[], int, int);
int bisearch(int[], int);

int main(void) {
int number[MAX] = {0};
int i, find;
srand(time(NULL));
for(i = 0; i < MAX; i++) {
number[i] = rand() % 100;
}
quicksort(number, 0, MAX-1);
printf("数列：");
for(i = 0; i < MAX; i++)
printf("%d ", number[i]);
printf("\n输入寻找对象：");
scanf("%d", &find);
if((i = bisearch(number, find)) >= 0)
printf("找到数字于索引 %d ", i);
else
printf("\n找不到指定数");
printf("\n");
return 0;
}
int bisearch(int number[], int find) {
int low, mid, upper;
low = 0;
upper = MAX - 1;
while(low <= upper) {
mid = (low+upper) / 2;
if(number[mid] < find)
low = mid+1;
else if(number[mid] > find)
upper = mid - 1;
else
return mid;
}
return -1;
}
void quicksort(int number[], int left, int right) {
int i, j, k, s;
if(left < right) {
s = number[(left+right)/2];
i = left - 1;
j = right + 1;
while(1) {
while(number[++i] < s) ; // 向右找
while(number[--j] > s) ; // 向左找
if(i >= j)
break;
SWAP(number[i], number[j]);
}

quicksort(number, left, i-1);// 对左边进行递回

quicksort(number, j+1, right); // 对右边进行递回
}
}

posted @ 2017-02-11 23:45  天秤libra  阅读(1198)  评论(0编辑  收藏