uva11549 Calculator Conundrum【解法二】

Alice got a hold of an old calculator that can display n digits. She
was bored enough to come up with the following time waster. She enters
a number k then repeatedly squares it until the result over ows. When
the result over ows, only the n most signi cant digits are displayed
on the screen and an error ag appears. Alice can clear the error and
continue squaring the displayed number. She got bored by this soon
enough, but wondered: \Given n and k , what is the largest number I
can get by wasting time in this manner?” Input The rst line of the
input contains an integer t (1  t  200), the number of test cases.
Each test case contains two integers n (1  n  9) and k (0  k< 10 n
) where n is the number of digits this calculator can display k is the
starting number. Output For each test case, print the maximum number
that Alice can get by repeatedly squaring the starting number as
described.

可以把【一个数->下一个数】看成链表，然后用floyd判圈算法，找到环时停止。

#include<cstdio>#include<cstring>#include<algorithm>using namespace std;#define LL long longint a[20],n;int ne(int x){    int l=0,ret=0,i;    LL t=(LL)x*x;    a[1]=0;    while (t)    {        a[++l]=t%10;        t/=10;    }    for (i=l;i&&i>=l-n+1;i--)      ret=ret*10+a[i];    return ret;}int main(){    int k,ans,T,i,x,y;    bool flag;    scanf("%d",&T);    while (T--)    {        scanf("%d%d",&n,&k);        ans=x=y=k;        do        {            x=ne(x);            y=ne(y);            ans=max(ans,y);            y=ne(y);            ans=max(ans,y);        }        while (x!=y);        printf("%d\n",ans);    }}