Jump Game II

public class Solution {
    public int jump(int[] A) {
        if(A == null){
            return 0;
        }
        int len = A.length;
        if(len == 0 || len == 1){
            return 0;
        }
        
        int cur = 0;
        int next = 0;
        int ret = 0;
        
        for(int i = 0; i < len; i++){
            if(i > cur){
                cur = next;
                ret++;
            }
            next = Math.max(next, i + A[i]);
        }
        return ret;
    }
}