update 3637 mod solution

java/search/BinarySearch3637.java

@@ -12,10 +12,14 @@ public class BinarySearch3637 {
         for (int i = 1; i < n; i++) {
             a.put(Integer.parseInt(args[i]));
         }
-        System.out.println(rightBound(x, a) - leftBound(x, a));
+        // System.out.println(rightBoundIterative(x, a) - leftBoundIterative(x, a));
+        System.out.println(
+            rightBoundRecursive(x, a, 0, a.getLength()) -
+                leftBoundRecursive(x, a, 0, a.getLength())
+        );
     }
 
-    static int leftBound(int x, IntList a) {
+    static int leftBoundIterative(int x, IntList a) {
         int low = 0,
             high = a.getLength() - 1;
         while (low <= high) {
@@ -29,7 +33,7 @@ public class BinarySearch3637 {
         return high + 1;
     }
 
-    static int rightBound(int x, IntList a) {
+    static int rightBoundIterative(int x, IntList a) {
         int low = 0,
             high = a.getLength() - 1;
         while (low <= high) {
@@ -43,47 +47,31 @@ public class BinarySearch3637 {
         return high + 1;
     }
 
-    static int searchIterativeDecreasing(int x, IntList a) {
+    static int leftBoundRecursive(int x, IntList a, int low, int high) {
-        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;
+            return high + 1;
         }
 
         int mid = low + (high - low) / 2;
 
-        if (a.get(mid) <= x) {
+        if (a.get(mid) > x) {
-            return searchRecursiveHelper(x, a, low, mid - 1);
+            return leftBoundRecursive(x, a, mid + 1, high);
         } else {
-            return searchRecursiveHelper(x, a, mid + 1, high);
+            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) {
+            rightBoundRecursive(x, a, mid + 1, high);
+        } else {
+            rightBoundRecursive(x, a, low, mid - 1);
         }
     }
 }