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斐波那契数列
题目:
大家都知道斐波那契数列,现在要求输入一个整数n,请你输出斐波那契数列的第n项(从0开始,第0项为0)。
n<=39
第一种想法:
使用递归的方法
public int Fibonacci(int n) {
if (n == 0) {
return 0;
}
if (n <= 2) {
return 1;
}
return Fibonacci(n - 1) + Fibonacci(n - 2);
}
第二种想法:
采用非递归的方法
public class Demo01 {
public static void main(String[] args) {
int x = 3;
int fibonacci = Fibonacci(x);
System.out.println(fibonacci);
}
public static int Fibonacci(int n) {
if (n == 0) {
return 0;
}
if (n <= 2) {
return 1;
}
int t1 = 1;
int t2 = 1;
int t3 = 0;
for (int i = 3; i <= n; i++) {
t3 = t2 + t1;
t1 = t2;
t2 = t3;
}
return t3;
}
}
第三种想法:
直接输出答案
public class Solution {
public int Fibonacci(int n) {
int a[] = {0,1,1,2,3,5,8,13,21,34,55,89,
144,233,377,610,987,1597,2584,
4181,6765,10946,17711,28657,
46368,75025,121393,196418,317811,
514229,832040,1346269,2178309,
3524578,5702887,9227465,14930352,
24157817,39088169,63245986};
return a[n];
}
}