Solution.java

package _004;

/**
 * <pre>
 *     author: Blankj
 *     blog  : http://blankj.com
 *     time  : 2017/10/12
 *     desc  :
 * </pre>
 */
public class Solution {
    public double findMedianSortedArrays(int[] nums1, int[] nums2) {
        int len = nums1.length + nums2.length;
        if (len % 2 == 0) {
            return (helper(nums1, 0, nums2, 0, len / 2) + helper(nums1, 0, nums2, 0, len / 2 + 1)) / 2.0;
        }
        return helper(nums1, 0, nums2, 0, (len + 1) / 2);
    }

    private int helper(int[] nums1, int m, int[] nums2, int n, int k) {
        if (m >= nums1.length) return nums2[n + k - 1];
        if (n >= nums2.length) return nums1[m + k - 1];
        if (k == 1) return Math.min(nums1[m], nums2[n]);

        int p1 = m + k / 2 - 1;
        int p2 = n + k / 2 - 1;
        int mid1 = p1 < nums1.length ? nums1[p1] : Integer.MAX_VALUE;
        int mid2 = p2 < nums2.length ? nums2[p2] : Integer.MAX_VALUE;
        if (mid1 < mid2) {
            return helper(nums1, m + k / 2, nums2, n, k - k / 2);
        }
        return helper(nums1, m, nums2, n + k / 2, k - k / 2);
    }

    public static void main(String[] args) {
        Solution solution = new Solution();
        System.out.println(solution.findMedianSortedArrays(
                new int[]{1, 3},
                new int[]{2}
        ));
        System.out.println(solution.findMedianSortedArrays(
                new int[]{1, 2},
                new int[]{3, 4}
        ));
    }
}