Find smallest missing number

src/main/java/com/spirecoder/SmallestMissingNumber.java

@@ -0,0 +1,41 @@
+package com.spirecoder;
+
+public class SmallestMissingNumber {
+
+    int findSmallestMissingSortedArray(int[] arr) {
+        if (arr[0] != 0)
+            return 0;
+
+
+        if (arr[arr.length - 1] == arr.length - 1)
+            return arr.length;
+
+        int first = arr[0];
+
+        return findFirstMissing(arr, 0,
+                arr.length - 1, first);
+    }
+
+    int findFirstMissing(int[] arr, int start, int end, int first) {
+
+        if (start < end) {
+            int mid = (start + end) / 2;
+            if (arr[mid] != mid + first)
+                return findFirstMissing(arr, start,
+                        mid, first);
+            else
+                return findFirstMissing(arr, mid + 1,
+                        end, first);
+        }
+        return start + first;
+
+    }
+
+    public static void main(String[] args) {
+        SmallestMissingNumber smallestMissingNumber = new SmallestMissingNumber();
+        int[] arr = {8, 1, 2, 3, 4, 5, 7};
+        int n = arr.length;
+
+        System.out.println("Missing element: " + smallestMissingNumber.findSmallestMissingSortedArray(arr));
+    }
+}

src/main/kotlin/com/spirecoder/SmallestMissingNumber.kt

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+package com.spirecoder
+
+import kotlin.jvm.JvmStatic
+import com.spirecoder.SmallestMissingNumber
+
+class SmallestMissingNumber {
+    fun findSmallestMissingSortedArray(arr: IntArray): Int {
+        if (arr[0] != 0) return 0
+        if (arr[arr.size - 1] == arr.size - 1) return arr.size
+        val first = arr[0]
+        return findFirstMissing(arr, 0,
+                arr.size - 1, first)
+    }
+
+    fun findFirstMissing(arr: IntArray, start: Int, end: Int, first: Int): Int {
+        if (start < end) {
+            val mid = (start + end) / 2
+            return if (arr[mid] != mid + first) findFirstMissing(arr, start,
+                    mid, first) else findFirstMissing(arr, mid + 1,
+                    end, first)
+        }
+        return start + first
+    }
+
+    companion object {
+        @JvmStatic
+        fun main(args: Array<String>) {
+            val smallestMissingNumber = SmallestMissingNumber()
+            val arr = intArrayOf(8, 1, 2, 3, 4, 5, 7)
+            val n = arr.size
+            println("Missing element: " + smallestMissingNumber.findSmallestMissingSortedArray(arr))
+        }
+    }
+}