Recursion and recursion

Recurrence ： Know the initial conditions , The initial condition is pushed upward until the target solution is obtained . The starting point of recursion is generally determined by the topic or the actual situation , Not derived from recursive relations . If the starting point of recursion cannot be determined , Then recursive algorithm cannot be realized . so , Recursive starting point is an important part of recursive algorithm .

Core code :

int main(){

cin>>N;

Bigint f[5010];

f[1]=Bigirt (1);

f[2]=Bigirt (2);

for (int i3=3;i<=N;i++）

f(i)=f(i-2）+f(i-1）;

f(N).print();

return 0;

}

recursive thinking ： Constructors , Call yourself when the function is running .

Recursive function is to call its own function , Often used to deal with factorials 、 Yang hui triangle 、 Fibonacci sequence, etc