【ZOJ4070】Function and Function（签到）

题意：求 k 层嵌套的 f(x)

0<=x,k<=1e9

思路：迭代不会很多次后函数里就会=0或者1，再看层数奇偶直接返回答案

#include<cstdio>
#include<cstring>
#include<string>
#include<cmath>
#include<iostream>
#include<algorithm>
#include<map>
#include<set>
#include<queue>
#include<vector>
using namespace std;
typedef long long ll;
typedef unsigned int uint;
typedef unsigned long long ull;
typedef pair<int,int> PII;
typedef vector<int> VI;
#define fi first
#define se second 
#define MP make_pair
#define N      110000
#define M      51
#define MOD 1000000007
#define eps 1e-8 
#define pi     acos(-1)
#define oo     1010000000

int a[10]={1,0,0,0,1,0,1,0,2,1};

int f(int n)
{
    int s=0;
    do{
        s+=a[n%10];
        n/=10;
    }while(n);
    return s;
}

int g(int n,int k)
{
    while(k--)
    {
        n=f(n);
        if(n==0) return k%2;
        if(n==1) return 1-k%2;
    }
    return n;
}

int main()
{ 
     int cas;
     scanf("%d",&cas);
     for(int v=1;v<=cas;v++) 
     {
        int n,k;
        scanf("%d%d",&n,&k);
        printf("%d
",g(n,k));
    }
    return 0;
}