LeetCode OJ 4. Median of Two Sorted Arrays

There are two sorted arrays nums1 and nums2 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)).

Example 1:

nums1 = [1, 3]
nums2 = [2]

The median is 2.0

Example 2:

nums1 = [1, 2]
nums2 = [3, 4]

The median is (2 + 3)/2 = 2.5

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【题目分析】

给定两个升序排列的整数数组，找到这两个数组所有元素的中位数。

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【思路】

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【java代码】

public class Solution {
    public double findMedianSortedArrays(int[] nums1, int[] nums2) {
        int[] A = nums1, B = nums2;
        int m = nums1.length, n = nums2.length;
        
        if(m > n){
            A = nums2; B = nums1;
            m = nums2.length; n = nums1.length;
        }
        
        if(n == 0) return 0;
        
        int mini = 0, maxi = m;
        int i = 0, j = 0;
        int maxofleft, minofright = 0;
        
        while(mini <= maxi){
            i = (maxi - mini)/2 + mini;
            j = (m + n + 1)/2 - i;
            if(j > 0 && i < m && B[j-1] > A[i]){
                mini = i + 1;
            }   //i is too small
            else if(i > 0 && j < n && A[i-1] > B[j]){
                maxi = i - 1;
            }   //i is too big
            else{
                if(i == 0) maxofleft = B[j-1];
                else if(j == 0) maxofleft = A[i-1];
                else maxofleft = Math.max(A[i-1], B[j-1]);
                
                if((m + n)%2 == 1) return maxofleft;
                
                if(i == m) minofright = B[j];
                else if(j == n) minofright = A[i];
                else minofright = Math.min(B[j], A[i]);
                
                return (double)(maxofleft + minofright) / 2.0;
            }
        }
        return 0;
    }
}