update README.md + update tests + add solution for hw2:3839

java/search/BinarySearch3839.java

@@ -0,0 +1,77 @@
+package search;
+
+/**
+ * @author Nikita Doschennikov (me@fymio.us)
+ */
+public class BinarySearch3839 {
+
+    public static void main(String[] args) {
+        IntList a = new IntList();
+        int x = Integer.parseInt(args[0]);
+        int n = args.length;
+        for (int i = 1; i < n; i++) {
+            a.put(Integer.parseInt(args[i]));
+        }
+
+        int leftBound = leftBoundIterative(x, a);
+        int rightBound = rightBoundIterative(x, a);
+        int range = rightBound - leftBound;
+        System.out.println(leftBound + " " + range);
+    }
+
+    static int leftBoundIterative(int x, IntList a) {
+        int low = 0,
+                high = a.getLength() - 1;
+        while (low <= high) {
+            int mid = low + (high - low) / 2;
+            if (a.get(mid) > x) {
+                low = mid + 1;
+            } else {
+                high = mid - 1;
+            }
+        }
+        return high + 1;
+    }
+
+    static int rightBoundIterative(int x, IntList a) {
+        int low = 0,
+                high = a.getLength() - 1;
+        while (low <= high) {
+            int mid = low + (high - low) / 2;
+            if (a.get(mid) >= x) {
+                low = mid + 1;
+            } else {
+                high = mid - 1;
+            }
+        }
+        return high + 1;
+    }
+
+    static int leftBoundRecursive(int x, IntList a, int low, int high) {
+        if (low > high) {
+            return high + 1;
+        }
+
+        int mid = low + (high - low) / 2;
+
+        if (a.get(mid) > x) {
+            return leftBoundRecursive(x, a, mid + 1, high);
+        } else {
+            return leftBoundRecursive(x, a, low, mid - 1);
+        }
+    }
+
+    static int rightBoundRecursive(int x, IntList a, int low, int high) {
+        if (low > high) {
+            return high + 1;
+        }
+
+        int mid = low + (high - low) / 2;
+
+        if (a.get(mid) >= x) {
+            return rightBoundRecursive(x, a, mid + 1, high);
+        } else {
+            return rightBoundRecursive(x, a, low, mid - 1);
+        }
+    }
+}