Median

 1 #include "stdafx.h"
 2 #include <iostream>
 3 #include   <vector>
 4 using namespace std;
 5 
 6 class Solution{
 7 public:
 8     double findMedianSortedArrays(int A[],int m, int B[],int n){
 9     if(m>n) findMedianSortedArrays(B,n,A,m);
10     int minidx=0,maxidx=m,i,j,num1,mid=(m+n+1)>>1,num2;
11     while(minidx<=maxidx)
12     {
13         i=(minidx+maxidx)>>1;
14         j=mid-i;
15         if(i<m&&j>0&&B[j-1]>A[i])minidx=i+1;  //取前面部分，如果B[j-1]>A[i],说明A[i]个肯定不含中位数，且中位数只会在A[i-1]的后面，因为B[j-1]多了大于的数，但总中位数的排序却不变
16         else if(i>0&&j<n&&A[i-1]>B[j])maxidx=i-1;   
17         else {
18         if(i==0)num1=B[j-1];
19         else if (j==0)num1=A[i-1];    //i,j 不可能取满
20         else num1=max(A[i-1],B[j-1]);  //可能A[i]=B[j-1]和A[i-1]=B[j]
21         break;
22         }
23 
24     }
25     if((m+n)&1)return num1;
26     if(i==m)num2=B[j];
27     else if(j==n)num2=A[i];
      else num2 = min(A[i],B[j]);  //偶数情况
28     return (num1+num2)/2;
29     
30     }    
31     
32 };
33 
34 int _tmain(int argc, _TCHAR* argv[])
35 {
36     Solution a;
37     int m,n,x;
38     int A[50],B[50];
39     cin>>m;
40     for(int i=0;i<m;i++){
41         cin>>x;
42         A[i]=x;
43     }
44         cin>>n;
45     for(int i=0;i<m;i++){
46         cin>>x;
47         B[i]=x;
48     }
49     
50 
51    cout<<a.findMedianSortedArrays(A,m,B,n);
52     
53 
54     system("pause");
55     return 0;
56     
57 
58 }

 1 class Solution{
 2 public:
 3 double findMedianSortedArrays(int A[],int m,int B[],int n){
 4 int total =m+n;
 5 if(total &0x1)
 6 return find_kth(A,m,B,n,total/2+1);
 7 else 
 8    return (find_kth(A,m,B,n,total/2)+find_kth(A,m,B,n,total/2+1))/2.0;
 9 }
10 private:
11   static int find_kth(int A[],int m,int B[],int n,int k);
12 {
13 if(m>n)return find_kth(B,n,A,m,k);
14 if(m==0)return B[k-1];
15 if(k==1)return min(A[0],B[0]);
16 int ia=min(k/2,m),ib=k-ia;
17 if(A[ia-1]<B[ib-1])
18   return find_kth(A+ia,m-ia,B,n,k-ia);
19  else if(A[ia-1]>B[ib-1])
20 return find_kth(A,m,B+ib,n-ib,k-ib);
21  else 
22   return A[ia-1];
23 }
24 }