Median of Two Sorted Arrays
<p>Given two sorted arrays <code>nums1</code> and <code>nums2</code> of size <code>m</code> and <code>n</code> respectively, return <strong>the median</strong> of the two sorted arrays.</p>

<p>The overall run time complexity should be <code>O(log (m+n))</code>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> nums1 = [1,3], nums2 = [2]
<strong>Output:</strong> 2.00000
<strong>Explanation:</strong> merged array = [1,2,3] and median is 2.
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> nums1 = [1,2], nums2 = [3,4]
<strong>Output:</strong> 2.50000
<strong>Explanation:</strong> merged array = [1,2,3,4] and median is (2 + 3) / 2 = 2.5.
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>nums1.length == m</code></li>
	<li><code>nums2.length == n</code></li>
	<li><code>0 &lt;= m &lt;= 1000</code></li>
	<li><code>0 &lt;= n &lt;= 1000</code></li>
	<li><code>1 &lt;= m + n &lt;= 2000</code></li>
	<li><code>-10<sup>6</sup> &lt;= nums1[i], nums2[i] &lt;= 10<sup>6</sup></code></li>
</ul>
Array; Binary Search; Divide and Conquer
public class Solution {
    private int m;
    private int n;
    private int[] nums1;
    private int[] nums2;

    public double FindMedianSortedArrays(int[] nums1, int[] nums2) {
        m = nums1.Length;
        n = nums2.Length;
        this.nums1 = nums1;
        this.nums2 = nums2;
        int a = f(0, 0, (m + n + 1) / 2);
        int b = f(0, 0, (m + n + 2) / 2);
        return (a + b) / 2.0;
    }

    private int f(int i, int j, int k) {
        if (i >= m) {
            return nums2[j + k - 1];
        }
        if (j >= n) {
            return nums1[i + k - 1];
        }
        if (k == 1) {
            return Math.Min(nums1[i], nums2[j]);
        }
        int p = k / 2;
        int x = i + p - 1 < m ? nums1[i + p - 1] : 1 << 30;
        int y = j + p - 1 < n ? nums2[j + p - 1] : 1 << 30;
        return x < y ? f(i + p, j, k - p) : f(i, j + p, k - p);
    }
}
