HDU 4394Digital Square

Digital Square

Time Limit : 2000/1000ms (Java/Other)   Memory Limit : 32768/32768K (Java/Other)

Total Submission(s) : 10   Accepted Submission(s) : 6

Problem Description

Given an integer N,you should come up with the minimum nonnegative integer M.M meets the follow condition: M²%10^x=N (x=0,1,2,3....)

 

Input

The first line has an integer T( T< = 1000), the number of test cases. For each case, each line contains one integer N(0<= N <=10[sup]9[/sup]), indicating the given number.

 

Output

For each case output the answer if it exists, otherwise print “None”.

 

Sample Input

3 3 21 25

 

Sample Output

None 11 5

 

Source

2012 Multi-University Training Contest 10

 

簡單搜索題，判斷幾位數相乘後對餘數沒有影響就好

#include<iostream>
#include<cstdio>
#include<cstring>
#include<queue>
using namespace std;

int t,n;
long long Mod;

struct node
{
    long long num;
    long long ten;
    friend bool operator < (node a,node b)
    {
        return a.num>b.num;
    }
} a,b;

void bfs()
{
    priority_queue<node>q;
    int num=n%10;
    for(int i=0; i<10; i++)
        if(i*i%10==num)
        {
            a.num=i;
            a.ten=10;
            q.push(a);
        }
    while(q.size())
    {
        a=q.top();
        if(a.num*a.num%Mod==n)
        {
            cout<<a.num<<endl;
            return ;
        }
        q.pop();
        for(long long i=0; i<10; i++)
        {
            b.num=a.num+i*a.ten;
            b.ten=a.ten*10;
            if(b.num*b.num%b.ten==n%b.ten)
            {
                q.push(b);
            }
        }
    }
    cout<<"None"<<endl;
    return ;
}

int main()
{
    scanf("%d",&t);
    while(t--)
    {
        cin>>n;
        int nn=n;
        Mod=1;
        while(nn)
        {
            Mod*=10;
            nn/=10;
        }
        bfs();
    }
}