斐波那契数列-递归层级是有限的,伪递归
public class Solution { public int Fib(int n) { if(n==0 || n ==1) return n; int[] cache = new int[n+1]; cache[0] = 0; cache[1] = 1; for(int i=2;i<=n;i++) { cache[i] = (cache[i-1]+cache[i-2])%1000000007; } return cache[n]; } public int FibCache(int n,int[] cache) { if(n == 0) return 0; if(n == 1) return 1; if(cache[n] != 0) return cache[n]; cache[n] = Fib(n-1) + Fib(n-2); return cache[n] % 1000000007; } }
--递归层数限制了,迭代去实现。斐波那契不是伪递归