查找算法——二分查找

一、C 程序实现

/*******************************************************************************************
*Description 二分查找算法
*Author liaoxiongxiong
*Version 1.0
*Time 2018-06-28
*******************************************************************************************/

#include <stdio.h>

//二分查找（折半查找），版本1
int BinarySearch1(int a[], int value, int n)
{
    int low, high, mid;
    low = 0;
    high = n-1;
    while(low<=high)
    {
        mid = (low+high)/2;
        if(a[mid] == value)
            return mid;
        if(a[mid]>value)
            high = mid-1;
        if(a[mid]<value)
            low = mid+1;
    }
    return -1;
}

//二分查找，递归版本
int BinarySearch2(int a[], int value, int low, int high)
{
    int mid = low+(high-low)/2;
    if(a[mid]==value)
        return mid;
    if(a[mid]>value)
        return BinarySearch2(a, value, low, mid-1);
    if(a[mid]<value)
        return BinarySearch2(a, value, mid+1, high);
    return -1;
}

//测试用例
int main()
{
    int a[]={0,1,2,3,4,5,6,7,8,9};
    int len = sizeof(a)/sizeof(a[0]);

    int x=2;   // 需要查找的元素

    int i = BinarySearch2(a, x, 0, len-1);
    if(i!=-1)
        printf("元素 %d 在第 %d 个位置\n",x,i+1);
    else
        printf("没有找到元素:%d\n",x);

    return 0;
}

运行结果：

 

二、Java 程序实现

/**
 * @description: 二分查找算法
 * @author： liaoxiongxiong
 * @version: 1.0
 * @date： 2018-06-28
 */


public class BinarySearch {
	
	//二分查找，版本1
	public static int binarySearch1(int[] a, int value, int n)
	{
		int low, high, mid;
	    low = 0;
	    high = n-1;
	    while(low<=high)
	    {
	        mid = (low+high)/2;
	        if(a[mid] == value)
	            return mid;
	        if(a[mid]>value)
	            high = mid-1;
	        if(a[mid]<value)
	            low = mid+1;
	    }
	    return -1;
	}
	
	//二分查找，版本2，递归式
	public static int binarySearch2(int[] a, int value, int low, int high)
	{
		int mid = (low+high)/2;
		while(low<=high)
		{
			if(a[mid] == value)
				return mid;
			if(a[mid] > value)
				return binarySearch2(a, value, low, mid-1);
			if(a[mid] < value)
				return binarySearch2(a, value, mid+1, low);
		}
		return -1;
	}
	
	//测试用例
		public static void main(String[] args)
		{
		    int[] a={0,1,2,3,4,5,6,7,8,9};
		    int len = a.length;

		    int x=2;   // 需要查找的元素

		    int i = binarySearch2(a, x, 0, len-1);
		    if(i!=-1)
		        System.out.printf("元素 %d 在第 %d 个位置\n",x,i+1);
		    else
		    	System.out.printf("没有找到元素:%d\n",x);
		    
		}

}

运行结果：

 

三、Python 程序实现

# -*- coding: utf-8 -*-
"""
Description: 二分查找算法
Author: shujuxiong
Version: 1.0
Date: 2018-06-28
"""

##二分查找，版本1
def binarySearch1(lists, value, n):
    low = 0;
    high = n-1;
    while(low <= high):
        mid = (low+high)//2
        if(lists[mid] == value):
            return mid;
        if(lists[mid] > value):
            high = mid-1
        if(lists[mid] < value):
            low = mid+1
    return -1


##二分查找，版本2，递归式
def binarySearch2(lists, value, low, high):
    mid = (low+high)//2
    if(lists[mid] == value):
        return mid;
    if(lists[mid] > value):
        return binarySearch2(lists, value, low, mid-1)
    if(lists[mid] < value):
        return binarySearch2(lists, value, mid+1, high)
    return -1


##测序用例
def main():
    mylist = [0,1,2,3,4,5,6,7,8,9]
    N = len(mylist)
    x = 2 #需要查找的元素
    i = binarySearch2(mylist, x, 0, N-1)
    if i != -1:
        print("元素 %d 在第 %d 个位置\n" % (x,i+1))
    else:
        print("没有找到元素:%d\n" % x)    
 
if __name__=='__main__':
    main()

运行结果：

 

转载于:https://www.cnblogs.com/shujuxiong/p/9240082.html