LeetCode-Median of Two Sorted Arrays

There are two sorted arrays A and B of size m and n respectively. Find the median of the two sorted arrays. The overall run time complexity should be O(log (m+n)).

 

class Solution {
public:
    int FindKthElm(int A[],int bA,int eA,int B[],int bB,int eB,int k){
        if(bA>eA){
            return B[bB+k-1];    
        }
        if(bB>eB){
            return A[bA+k-1];
        }
        int mA=(bA+eA)/2;
        int mB=(bB+eB)/2;
        int half=mA-bA+mB-bB+2;
        if(A[mA]>B[mB]){
 //此时B数组和第k元素都在A[mA]左侧，A[mA]到A[eA]可以舍弃
            if(k<half){
                return FindKthElm(A,bA,mA-1,B,bB,eB,k);
            }
 //此时k元素及A数组都在B[mB]右侧，B[bB]到B[mB]可以舍弃
            else{
                return FindKthElm(A,bA,eA,B,mB+1,eB,k-(mB-bB+1));
            }
        }
        else if(A[mA]==B[mB]){
			if(k<=half-2){
				return FindKthElm(A,bA,mA-1,B,bB,mB-1,k);
			}
			else if(k>half){
				return FindKthElm(A,mA+1,eA,B,mB+1,eB,k-(half));
			}
			else return A[mA];
		}
        else{
 //此时A数组和第k元素都在B[mB]左侧，B[mB]到B[eB]可以舍弃
            if(k<half){
                return FindKthElm(A,bA,eA,B,bB,mB-1,k);
            }
 //此时k元素及B数组都在A[mA]右侧，A[bA]到A[mA]可以舍弃
            else{
                return FindKthElm(A,mA+1,eA,B,bB,eB,k-(mA-bA+1));
            }
        }
    }
    double findMedianSortedArrays(int A[], int m, int B[], int n) {
        int total=m+n;
        if(total==0)return 0;
        if(total%2==0){
            int index1=total/2+1;
            int index2=index1-1;
		    int val1=FindKthElm(A,0,m-1,B,0,n-1,index1);
	    	int val2=FindKthElm(A,0,m-1,B,0,n-1,index2);
           return (val1+val2)/2.0;
        }
        else{
            return FindKthElm(A,0,m-1,B,0,n-1,total/2+1);
        }
    }
};            

 

public class Solution {
   public int FindKth(int A[],int B[],int sa,int ea,int sb,int eb,int k){
        if(sa>ea){
            return B[sb+k-1];
        }
        else if(sb>eb){
            return A[sa+k-1];
        }
        else{
            int midA=(sa+ea)/2;
            int midB=(sb+eb)/2;
            int half=midA-sa+midB-sb+2;
            if(A[midA]>B[midB]){
                if(k<half)return FindKth(A,B,sa,midA-1,sb,eb,k);
                else return FindKth(A,B,sa,ea,midB+1,eb,k-(midB-sb+1));
            }
            else if(A[midA]<B[midB]){
                if(k<half)return FindKth(A,B,sa,ea,sb,midB-1,k);
                else return FindKth(A,B,midA+1,ea,sb,eb,k-(midA-sa+1));
            }
            else{
                if(k>half){
                    k-=half;
                    return FindKth(A,B,midA+1,ea,midB+1,eb,k);
                }
                else if(k<half-2){
                    return FindKth(A,B,sa,midA-1,sb,midB-1,k);
                }
                else return A[midA];
            }
        }
    }
    public double findMedianSortedArrays(int A[], int B[]) {
        // Note: The Solution object is instantiated only once and is reused by
        // each test case.
        int total=A.length+B.length;
        if(total==0)return 0;
        if(total%2==0){
            int p1=FindKth(A,B,0,A.length-1,0,B.length-1,total/2);
            int p2=FindKth(A,B,0,A.length-1,0,B.length-1,total/2+1);
            return (p1+p2*1.0)/2;
        }
        else{
            return FindKth(A,B,0,A.length-1,0,B.length-1,total/2+1);
        }
        
    }
}