問題及代碼:
/*
* Copyright(c) 2017,煙臺大學計算機學院
* All rights reserved.
* 文件名稱:cpp1.
* 作 者:薛瑞琪
* 完成日期:2017 年 11 月 23 日
* 版 本 號:v1.0
*
* 問題描述: 認真閱讀並驗證折半查找算法。請用有序表{12,18,24,35,47,50,62,83,90,115,134}作爲測試序列,分別對查找90、47、100進行測試。
* 輸入描述:無需輸入
* 程序輸出:實現各種算法的函數的測試結果
*/
1.折半查找
#include <stdio.h>
#define MAXL 100
typedef int KeyType;
typedef char InfoType[10];
typedef struct
{
KeyType key; //KeyType爲關鍵字的數據類型
InfoType data; //其他數據
} NodeType;
typedef NodeType SeqList[MAXL]; //順序表類型
int BinSearch(SeqList R,int n,KeyType k)
{
int low=0,high=n-1,mid;
while (low<=high)
{
mid=(low+high)/2;
if (R[mid].key==k) //查找成功返回
return mid+1;
if (R[mid].key>k) //繼續在R[low..mid-1]中查找
high=mid-1;
else
low=mid+1; //繼續在R[mid+1..high]中查找
}
return 0;
}
int main()
{
int i,n=10;
int result;
SeqList R;
KeyType a[]= {12,18,24,35,47,50,62,83,90,115,134},x=90,y=47,z=100;
for (i=0; i<n; i++)
R[i].key=a[i];
result = BinSearch(R,n,x);
if(result>0)
printf("序列中第 %d 個是 %d\n",result, x);
else
printf("木有找到!\n");
result = BinSearch(R,n,y);
if(result>0)
printf("序列中第 %d 個是 %d\n",result, y);
else
printf("木有找到!\n");
result = BinSearch(R,n,z);
if(result>0)
printf("序列中第 %d 個是 %d\n",result, z);
else
printf("木有找到!\n");
return 0;
}
2.遞歸的折半查找
#include <stdio.h>
#define MAXL 100
typedef int KeyType;
typedef char InfoType[10];
typedef struct
{
KeyType key; //KeyType爲關鍵字的數據類型
InfoType data; //其他數據
} NodeType;
typedef NodeType SeqList[MAXL]; //順序表類型
int BinSearch1(SeqList R,int low,int high,KeyType k)
{
int mid;
if (low<=high) //查找區間存在一個及以上元素
{
mid=(low+high)/2; //求中間位置
if (R[mid].key==k) //查找成功返回其邏輯序號mid+1
return mid+1;
if (R[mid].key>k) //在R[low..mid-1]中遞歸查找
BinSearch1(R,low,mid-1,k);
else //在R[mid+1..high]中遞歸查找
BinSearch1(R,mid+1,high,k);
}
else
return 0;
}
int main()
{
int i,n=10;
int result;
SeqList R;
KeyType a[]= {12,18,24,35,47,50,62,83,90,115,134},x=90,y=47,z=100;
for (i=0; i<n; i++)
R[i].key=a[i];
result = BinSearch1(R,0,n-1,x);
if(result>0)
printf("序列中第 %d 個是 %d\n",result, x);
else
printf("木有找到!\n");
result = BinSearch1(R,0,n-1,y);
if(result>0)
printf("序列中第 %d 個是 %d\n",result, y);
else
printf("木有找到!\n");
result = BinSearch1(R,0,n-1,z);
if(result>0)
printf("序列中第 %d 個是 %d\n",result, z);
else
printf("木有找到!\n");
return 0;
}
運行結果:
知識的總結:
折半算法
學習心得:
運行並本週視頻中所講過的算法,觀察結果並領會算法