MissingInteger

tab1

Task Score     :100
Correctness   :100
Performance : 100

Task description

This is a demo task.

Write a function:

class Solution { public int solution(int[] A); }

that, given an array A of N integers, returns the smallest positive integer (greater than 0) that does not occur in A.

For example, given A = [1, 3, 6, 4, 1, 2], the function should return 5.

Given A = [1, 2, 3], the function should return 4.

Given A = [−1, −3], the function should return 1.

Write an efficient algorithm for the following assumptions:

• N is an integer within the range [1..100,000];
• each element of array A is an integer within the range [−1,000,000..1,000,000].

Solution

import java.util.Arrays;

public class MissingInteger {

 public static void main(String[] args) {

  int[] A = { 1, 3, 6, 4, 1, 2 };
  System.out.println(new MissingInteger().solution(A));
 }

 public int solution(int[] A) {

  Arrays.sort(A);

  if (A.length == 0) {
   return 1;
  }

  if (A.length == 1 && A[0] != 1) {
   return 1;
  }

  if (A[A.length - 1] < 1) {
   return 1;
  }

  int[] t = new int[A[A.length - 1] + 1]; //Temp array to mark occurences
  for (int i : A) {
   if (i < 1) {
    continue;
   }
   t[i] = t[i] + 1;
  }
  for (int i = 0; i < t.length; i++) {
   if (i > 0 && t[i] == 0) {
    return i;
   }
  }
  return A[A.length - 1] + 1;
 }
}