[演算法,分治]二分搜尋法

二分搜尋法每次將搜尋空間縮小一倍,其最大搜尋長度為:log[n]+1

bool binarySearch(int target,int tmpArr[],int length)
{
 int l,u,m;
 l=0;
 u=length-1;
 while(l<=u)
 {
  m=(l+u)/2;
  if(tmpArr[m]>target)u=m-1;
  else if(tmpArr[m]==target)return true;
  else        l=m+1;
 }
 return false;
}

測試程式:

#include <iostream.h>

void swap(int &a,int &b);
void simpleSort(int tmpArr[],int length);
void showArr(int tmpArr[],int length);
bool binarySearch(int target,int tmpArr[],int length);

int main()
{
 int arr[10]={8,7,5,4,2,3,10,11,21,87};
 int len=10;
 int target=4;
 simpleSort(arr,len);
 showArr(arr,len);
 if(binarySearch(target,arr,len))
  cout<<"target:"<<target<<"was found."<<endl;
 else
  cout<<"target:"<<target<<"was not found."<<endl;
 return 1;
}

void swap(int &a,int &b)
{
 int tmp=a;
 a=b;
 b=tmp;
}

void simpleSort(int tmpArr[],int length)
{
 int i=0,j=0;
 for(i=length-1;i>0;i--)
  for(j=0;j<i;j++)
   if(tmpArr[j]>tmpArr[j+1])swap(tmpArr[j],tmpArr[j+1]);
}

void showArr(int tmpArr[],int length)
{
 cout<<"[";
 int i=0;
 for(;i<length-1;i++)
  cout<<tmpArr[i]<<",";
 cout<<tmpArr[length-1]<<"]"<<endl;
}