[CountingElements] Codility-MissingInteger

Author: Seogeurim

README.md

@@ -52,6 +52,7 @@
 | 02  |     | [Codility-Lesson2 OddOccurrencesInArray](./src/Array/OddOccurrencesInArray) |      |
 | 03  |     | [Codility-Lesson4 FrogRiverOne](./src/Array/FrogRiverOne)                   |      |
 | 04  |     | [Codility-Lesson4 PermCheck](./src/Array/PermCheck)                         |      |
+| 05  |     | [Codility-Lesson4 MissingInteger](./src/Array/MissingInteger)               |      |
 
 ### Stack
 

src/Array/MissingInteger/Main.java

@@ -0,0 +1,22 @@
+package Array.MissingInteger;
+
+public class Main {
+    public static void main(String[] args) {
+        Solution sol = new Solution();
+        System.out.println(sol.solution(new int[]{1, 2, 3}));
+    }
+}
+
+class Solution {
+
+    static boolean[] check = new boolean[1000001];
+
+    public int solution(int[] A) {
+        for (int value : A) {
+            if (value > 0) check[value] = true;
+        }
+        int ans = 1;
+        while (check[ans]) ans ++;
+        return ans;
+    }
+}

src/Array/MissingInteger/README.md

@@ -0,0 +1,5 @@
+## [Codility - Lesson 4 Counting Elements] MissingInteger
+
+> Detected time complexity : **O(N) or O(N * log(N))**
+
+![image](https://user-images.githubusercontent.com/22045163/104467349-9205bf80-55f9-11eb-9944-5a0ce4077b19.png)