斐波那契数列

public class Solution12 {
    public static int Fibonacci(int n){ //输入为第N项，返回值为第N项的值
        int a=1; int b=1; int c=0;
        if (n <=0){
            return 0;
        }else if (n==1||n==2){
            return 1;
        }else {
            for (int i=3;i<=n;i++){ //在执行第二轮循环的时候a,b的值分别赋为上一轮b,c的值
                c = a+b;
                b = a;
                a = c;
            }
        }
        return c;
    }
    public static void main(String args[]){
        System.out.println(Fibonacci(39));
    }
}
//输出：
//63245986
//
//Process finished with exit code 0