剑指10-2 青蛙跳台阶

剑指10-2 青蛙跳台阶

class Solution {
    public int numWays(int n) {
        if (n == 0)
            return 1;
        if (n == 1)
            return 1;
        if (n == 2)
            return 2;
        int[] dp = new int[n + 1];
        dp[0] = 1; dp[1] = 1; dp[2] = 2;
        for (int i = 3; i <= n; i++) {
            dp[i] = dp[i - 1] + dp[i - 2];
            dp[i] %= 1e9+7;
        }
        return dp[n];
    }
}