折半查找法

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

#define max_num		100
#define SWAP(X, Y, TEMP)	((TEMP = X), (X = Y), (Y = TEMP))

int main(int argc, char *argv[])
{
	int list[max_num];
	int i, j, num, min, temp;
	int mid, left = 0, right = 0, find_data, find_flag = -1;
	
	printf("Please input number:");
	scanf("%d", &num);
	if (num < 0 || num > max_num) {
		fprintf(stderr, "invalid data\n");
		exit(1);
	}
	for (i = 0; i < num; i++) {
		list[i] = rand() % 1000;
		printf("%d  ", list[i]);
	}
	printf("\n");

	for (i = 0; i < num; i++) {
		min = i;
		for (j = i + 1; j < num; j ++) {
			if (list[j] < list[min])
				min = j;
		}
		SWAP(list[i], list[min], temp);
	}
	
	printf("After select sort result:\n");
	for (i = 0; i < num; i ++)
		printf("%d  ", list[i]);	
	printf("\n");

	printf("Please input find data:");
	scanf("%d", &find_data);
	
	right = num - 1;
	while (left <= right) {
		mid = (left + right) / 2;
		if (list[mid] == find_data) {
			find_flag = mid;
			break;
		} else if (list[mid] < find_data) {
			left = mid + 1;
		} else 
			right = mid - 1;
	}
	if (find_flag != -1) {
		printf("Find data is sign: %d\n", find_flag);
	}
}

折半查找法

原文：http://blog.csdn.net/chenliang0224/article/details/18995189