45 Jump Game ii

DP 

public class Solution {
    public int jump(int[] A) {
        if (A == null || A.length == 0) {
            return 0;
        }
        
        int reach = 0;
        int lastreach = 0;
        int step = 0;
        
        for (int i = 0; i < A.length && i <= reach; i++) {
            if (i > lastreach) {
                step++;
                lastreach = reach;
            }
            reach = Math.max(reach, A[i] + i);
        }
        if (reach < A.length - 1) {
            return 0;
        }
        return step;
    }
}