[图解算法] 二分查找Binary-Search——<递归与分治策略>

 1 #include"iostream.h"
 2 
 3 int BinarySearch(int a[],int left,int right,const int& x)
 4 {
 5     if(left<right)
 6     {
 7         int middle = (left+right)/2;
 8         if(x==a[middle]) return middle;
 9         if(x>a[middle]) return BinarySearch(a,middle+1,right,x);
10         else return BinarySearch(a,left,middle-1,x);
11     }
12 }
13 
14 void main(){
15     int n,x,i,a[99];
16     cout<<"input the length of a[]"<<endl;
17     cin>>n;
18     cout<<"input array a[]"<<endl;
19     for(i=0;i<n;i++) cin>>a[i];
20     cout<<"input the num u want to find"<<endl;
21     cin>>x;
22     cout<<BinarySearch(a,0,n-1,x)+1<<endl;
23 }

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