经典题find median of two sorted array

10/30

大概写了15分钟， 3个错， 两个typo， 一个参数，不合格！

public class Solution {
    public double findMedianSortedArrays(int A[], int B[]) {
        int lenA = A.length, lenB = B.length;
        int len = (lenA+lenB);
        if(len%2 == 1){ //err1: typo lenA for len
            return findKthInArray(len/2+1,A,0,lenA,B,0,lenB);
        }else{
            return (findKthInArray(len/2,A,0,lenA,B,0,lenB) + findKthInArray(len/2+1,A,0,lenA,B,0,lenB))/2.0;
        }
    }
    
    public int findKthInArray(int k, int[] A, int startA, int lenA, int[] B, int startB, int lenB){
        // note that lenA <= lenB
        if(lenA > lenB){
            return findKthInArray(k,B,startB,lenB,A,startA,lenA);
        }
        
        // now lenA <= lenB
        if(lenA == 0)       return B[startB+k-1];
        else if(k==1)       return Math.min(A[startA],B[startB]);
        
        int pA = Math.min(k/2, lenA); //pA <= k/2 <= pB
        int pB = k-pA;
        
        int checkA = startA + pA - 1; // err2: lenA for startA
        int checkB = startB + pB - 1;
        
        if(A[checkA] == B[checkB])
            return A[checkA];
        else if(A[checkA] < B[checkB])
            return findKthInArray(k-pA,A, checkA+1, lenA-pA, B, startB, lenB);
        else
            return findKthInArray(k-pB, A, startA, lenA, B, checkB + 1, lenB-pB); // err3: forget about -pB and -pA
        
    }
}