UVA 10696 - f91

Problem A - f91

Time Limit: 1 second

Background

McCarthy is a famous theorician of computer science. In his work, he defined a recursive function, called f91, that takes as input a positive integer N and returns a positive integer defined as follows:

• If N ≤ 100, then f91(N) = f91(f91(N+11));
• If N ≥ 101, then f91(N) = N-10.

The Problem

Write a program, that computes McCarthy's f91.

The Input

The input tests will consist of a series of positive integers, each integer is at most 1,000,000. There will be at most 250,000 test cases. Each number is on a line on its own. The end of the input is reached when the number 0 is met. The number 0 shall not be considered as part of the test set.

Output

The program shall output each result on a line by its own, following the format given in the sample output.

Sample input

500910

Sample output

f91(500) = 490f91(91) = 91

本来以为这题还得推一下递推关系式再打表呢，结果直接递归打表都不会T

不过用了0.8s，差点就T掉了。

#include<cstdio>#include<iostream>#include<string>#include<vector>#include<map>#include<set>#include<algorithm>#include<cmath>#include <cstring>#include <queue>using namespace std;#define eps 1e-20#define MAXN 1000000 + 10#define outstars cout << "*********" << endl;int f[MAXN];int ff(int n){    if(n <= 100)    {        return ff(ff(n + 11));    }    else return n - 10;}int main(){    int n;    for(int i = 1 ; i <= 1000000 ; i++)    {        f[i] = ff(i);        //cout << f[i] << endl;    }    while(cin >> n , n)    {        printf("f91(%d) = %d\n",n,f[n]);    }    return 0;}/**/