【leetcode】青蛙跳台阶问题

实际就是求斐波那契数列

int numWays(int n){
    if (n == 0 || n == 1)
        return 1;
    int prepre = 1;
    int pre = 1;
    int curr = 0;
    for (int i = 2; i <= n; i++)
    {
        curr = prepre + pre;
        curr %= 1000000007;
        prepre = pre;
        pre = curr;
        //printf("%u--%d\n", curr, i);
    }
    return curr;
}

int count =0;
void one(int n,int sum);
void two(int n,int sum);

void one(int n,int sum)
{
    sum+=1;
    if (sum == n)
        count++;
    else if(sum < n)
    {
        one(n,sum);
        two(n,sum);
    }
}
void two(int n,int sum)
{
    sum+=2;
    if (sum == n)
        count++;
    else if(sum < n)
    {
        one(n,sum);
        two(n,sum);
    }
}
int numWays(int n){
    if (n == 0 || n == 1)
        return 1;
    int sum =0;
    one(n,sum);
    two(n,sum);

    return count;
}