剑指 Offer 10- II. 青蛙跳台阶问题

动态规划

public int numWays(int n) {
        if(n == 0 || n == 1) return 1;
        int[] dp = new int[n+1];
        dp[0] = 1;
        dp[1] = 1;
        for(int i = 2;i<=n;i++){
            int m = dp[i - 1] + dp[i - 2];
            if(i>=44){
                dp[i] = m %1000000007;
            }else {
                dp[i] = m;
            }
        }
        return dp[n];
    }