Find the minimal positive integer not occurring in a given sequence.

MissingInteger.java

public class MissingInteger {
	public int minMissingInteger(int[] A) {
		if(A == null || A.length == 0) {
			return -1;
		}
		
		int[] items = new int[A.length + 1];
		for(int i = 0; i < items.length; i++) {
			items[i] = -1;
		}
		
		for(int i = 0; i < A.length; i++) {
			int item = A[i];
			if(item > 0 && item <= (A.length + 1)) {
				items[item - 1] = 1;
			}
		}
		
		for(int i = 0; i < items.length; i++) {
			if(items[i] == -1) {
				return i + 1;
			}
		}

		return -1;
	}
}