常用数据结构与算法之查找算法

查找算法

/*
 * =====================================================================================
 *
 *       Filename:  search.h
 *
 *    Description:  template function of search algo
 *
 *        Version:  1.0
 *        Created:  2012年04月15日 16时28分42秒
 *       Revision:  none
 *       Compiler:  gcc
 *
 *         Author:  Lavey Luo (lavey), [email protected]
 *   Organization:  
 *
 * =====================================================================================
 */
#ifndef __SEARCH_H_
#define __SEARCH_H_
namespace stcpp
{
		/* 顺序查找 */
	template<class T>
		int sequence_search(T a[],  int len,  T key) 
		{
			for (int i = 0; i < len; i++ )
			{
				if (a[i] == key)
					return i;
			}
			return -1;
		}

	/* 二分查找 */
	template<class T>
	int binary_search(T a[],  int len,  T key) 
	{
		int low  = 0;
		int high = len -1;
		while (low <= high)
		{
			int mid = (low + high)/2;/* 折半 */
			if (a[mid] < key)
			{
				low = mid + 1;
			}
			else if (a[mid] > key)
			{
				high = mid -1;
			}
			else
				return mid;
		}
		return -1;
	}

/* 插值查找 */
	template<class T>
	int interpolation_search(T a[],  int len,  T key) 
	{

		int low  = 0;
		int high = len -1;
		while (low <= high)
		{
			int mid = low + (high - low)*(key - a[low])/(a[high] - a[low]);
			if (a[mid] < key)
			{
				low = mid + 1;
			}
			else if (a[mid] > key)
			{
				high = mid -1;
			}
			else
				return mid;
		}
		return -1;
	}
/* 斐波那契查找 */
	template<class T>
		int Fibonacci_Search(T a[], int n, T key)
		{
			int i,k=0;
			int low = 0;	/* 定义最低下标为记录首位 */
			int high = n -1;	/* 定义最高下标为记录末位 */

			/* 构建 斐波那契 数组*/
			int F[100] = {0};
			F[0] = 0;
			F[1] = 1;
			for (i=2; i<100; i++)
				F[i] = F[i-1] + F[i-2];
			
			/* 计算n位于斐波那契数列的位置 */
			while(n > F[k]-1)
				k++;
			/* 将不满 的数值以最后一个元素的值补全 */
			for (i= n - 1; i < F[k]-1; i++)
				a[i]=a[n -1];

			while(low <= high)
			{
				int mid=low + F[k-1]-1;
				if (key < a[mid])
				{
					high = mid - 1;		
					k = k-1;
				}
				else if (key > a[mid])
				{
					low = mid + 1;		
					k = k - 2;
				}
				else
				{
					if (mid <= n - 1)
						return mid;		/* 若相等则说明mid即为查找到的位置 */
					else 
						return -1;
				}
			}
			return -1;
		}
}
#endif //__SEARCH_H_

测试用例

/*
 * =====================================================================================
 *
 *       Filename:  test_search.cpp
 *
 *    Description:  test case of the search.h
 *
 *        Version:  1.0
 *        Created:  2012年04月15日 17时41分26秒
 *       Revision:  none
 *       Compiler:  gcc
 *
 *         Author:  Lavey Luo (lavey), [email protected]
 *   Organization:  
 *
 * =====================================================================================
 */
#include "search.h"
#include <iostream>
using std::cout;
using std::endl;

int test_search(int argc,  char** argv)
{
	 int a[]  = {2, 6, 4, 3, 1, 5};
	 const unsigned int len  = sizeof(a)/sizeof(int);

	 int b[]  = {2, 4, 8, 10, 50, 88};
	 int key = 4;
	 int idx = stcpp::sequence_search(a, len, key);
	 cout << "sequence_search: idx of " << key << " is " << idx << endl;;

	 key = 10;
	 idx = stcpp::binary_search(b, len, key);
	 cout << "binary_search: idx of " << key << " is " << idx << endl;


	 key = 8;
	 idx = stcpp::interpolation_search(b, len, key);
	 cout << "interpolation_search: idx of " << key << " is " << idx << endl;
	 
	 key = 50;
	 idx = stcpp::Fibonacci_Search(b, len, key);
	 cout << "Fibonacci_Search: idx of " << key << "  is " << idx << endl;
	 return 0;
}