HDOJ 题目4394 Digital Square（DFS）

Digital Square

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 1757    Accepted Submission(s): 677

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 <=10⁹), indicating the given number.

 

Output

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

 

Sample Input

332125

 

Sample Output

None115

 

Source

2012 Multi-University Training Contest 10

 

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ac代码

#include<stdio.h>#include<string.h>#define INF 1<<30#define max(a,b) (a>b?a:b)#define min(a,b) (a>b?b:a)int a[20];__int64 mod[20],ans,n,len;void init(){mod[0]=1;for(int i=1;i<20;i++){mod[i]=mod[i-1]*10;}}void fun(){__int64 temp=n;len=0;memset(a,0,sizeof(a));while(temp){a[len++]=temp%10;temp/=10;}}void dfs(int now,int step){if(step==len){ans=min(ans,now);return;}for(int i=0;i<=9;i++){__int64 to,temp=now+mod[step]*i;to=temp;temp*=temp;temp/=mod[step];temp%=10;if(temp==a[step]){dfs(to,step+1);}}}int main(){int t;init();scanf("%d",&t);while(t--){scanf("%I64d",&n);fun();ans=INF;dfs(0,0);if(ans==INF){printf("None\n");}elseprintf("%d\n",ans);}}