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];
}
}