add 3637 mod + tests

java/search/BinarySearch3637.java

@@ -0,0 +1,88 @@
+package search;
+
+/**
+ * @author Nikita Doschennikov (me@fymio.us)
+ */
+public class BinarySearch3637 {
+
+    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]));
+        }
+
+        System.out.println(
+            searchIterativeIncreasing(x, a.getReversed()) -
+                searchIterativeDecreasing(x, a)
+        );
+    }
+
+    static int searchIterativeIncreasing(int x, IntList a) {
+        if (a.getLength() == 0) {
+            return 0;
+        }
+
+        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 low;
+    }
+
+    static int searchIterativeDecreasing(int x, IntList a) {
+        if (a.getLength() == 0) {
+            return 0;
+        }
+
+        int low = 0,
+            high = a.getLength() - 1;
+
+        while (low <= high) {
+            int mid = low + (high - low) / 2;
+
+            if (a.get(mid) <= x) {
+                high = mid - 1;
+            } else {
+                low = mid + 1;
+            }
+        }
+
+        return low;
+    }
+
+    static int searchRecursive(int x, IntList a) {
+        return searchRecursiveHelper(x, a, 0, a.getLength() - 1);
+    }
+
+    private static int searchRecursiveHelper(
+        int x,
+        IntList a,
+        int low,
+        int high
+    ) {
+        if (low > high) {
+            return low;
+        }
+
+        int mid = low + (high - low) / 2;
+
+        if (a.get(mid) <= x) {
+            return searchRecursiveHelper(x, a, low, mid - 1);
+        } else {
+            return searchRecursiveHelper(x, a, mid + 1, high);
+        }
+    }
+}