变态跳台阶

变态跳台阶

public class Solution {
    public int JumpFloorII(int target) {
        if(target <= 2) return target;
        int[] v = new int[target + 1];
        v[1] = 1;
        v[2] = 2;
        return f(target, v);
    }
    int f(int target, int[] v){
        int sum = 1;
        for(int i = 1; i < target; ++i){
            if(v[i] == 0){
                int temp = f(i, v);
                v[i] = temp;
            }
            sum += v[i];
        }
        return sum;
    }
}