Added Java solution for "Search a 2D Matrix"

Author: Kyrylo-Ktl

Java/Search a 2D Matrix.java

@@ -0,0 +1,27 @@
+public class Solution {
+
+    /**
+     * Time:   O(log(n*m))
+     * Memory: O(1)
+     */
+    public boolean searchMatrix(int[][] matrix, int target) {
+        int n = matrix.length, m = matrix[0].length;
+        int left = 0, right = n * m - 1;
+
+        while (left <= right) {
+            int mid = (left + right) / 2;
+            int num = matrix[mid / m][mid % m];
+
+            if (num == target)
+                return true;
+
+            if (num < target) {
+                left = mid + 1;
+            } else {
+                right = mid - 1;
+            }
+        }
+
+        return false;
+    }
+}