剑指offer（9）变态跳台阶
public class Solution {
public int JumpFloorII(int target) {
if(target < 0){
return -1;
}else if(target == 0){
return 0;
}else if(target == 1){
return 1;
}else{
return 2*JumpFloorII(target - 1);
}
}
}
