update 4.median_of_two_sorted_arrays.java

Author: marklcrns

4.median_of_two_sorted_arrays.java

@@ -0,0 +1,61 @@
+/**
+ * Resources:   https://www.youtube.com/watch?v=lLFDQCDzfpI
+ *              https://www.geeksforgeeks.org/merge-two-sorted-arrays/
+ */
+class Solution {
+	public double findMedianSortedArrays(int[] nums1, int[] nums2) {
+		// Ensure nums1 has the greater length
+		if (nums1.length > nums2.length) {
+			int [] tmp = nums1;
+			nums1 = nums2;
+			nums2 = tmp;
+		}
+
+		int lo = 0;
+		int hi = nums1.length;
+		int combinedLen = nums1.length + nums2.length;
+
+		while (lo <= hi) {
+			int partX = (lo + hi) / 2;
+			int partY = (combinedLen + 1) / 2 - partX;
+
+			int leftX = getMax(nums1, partX);
+			int rightX = getMin(nums1, partX);
+
+			int leftY = getMax(nums2, partY);
+			int rightY = getMin(nums2, partY);
+
+			if (leftX <= rightY && leftY <= rightX) {
+				if (combinedLen % 2 == 0) {
+					return (Math.max(leftX, leftY) + Math.min(rightX, rightY)) / 2.0;
+				}
+				return Math.max(leftX, leftY);
+			}
+
+			if (leftX > rightY) {
+				hi = partX - 1;
+			} else {
+				lo = partX + 1;
+			}
+
+		}
+
+		return -1;
+	}
+
+	private int getMax(int[] nums, int partition) {
+		if (partition == 0) {
+			return (int)Double.NEGATIVE_INFINITY;
+		} else {
+			return nums[partition - 1];
+		}
+	}
+
+	private int getMin(int[] nums, int partition) {
+		if (partition == nums.length) {
+			return (int)Double.POSITIVE_INFINITY;
+		} else {
+			return nums[partition];
+		}
+	}
+}