Find the earliest time when a frog can jump to the other side of a river.

FrogRiverOne.java

public class FrogRiverOne {
	public int solution(int X, int[] A) {
		if(A == null || A.length == 0) {
			return -1;
		}
		
		int[] passed = new int[X];
		for(int i = 1; i <= passed.length; i++) {
			passed[i-1] = -1;
		}
		
		int missing = X;
		
		for(int i = 0; i < A.length; i++) {
			if(passed[A[i] -1] != -1) {
				continue;
			} else {
				passed[A[i] -1] = i;
				missing -= 1;
				if(missing == 0) {
					return i;
				}
			}
		}
		
		return -1;
	}
}