hdu 1015 Safecracker

Safecracker

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/32768 K (Java/Others)
Total Submission(s): 15156    Accepted Submission(s): 7991

Problem Description

=== Op tech briefing, 2002/11/02 06:42 CST === 
"The item is locked in a Klein safe behind a painting in the second-floor library. Klein safes are extremely rare; most of them, along with Klein and his factory, were destroyed in World War II. Fortunately old Brumbaugh from research knew Klein's secrets and wrote them down before he died. A Klein safe has two distinguishing features: a combination lock that uses letters instead of numbers, and an engraved quotation on the door. A Klein quotation always contains between five and twelve distinct uppercase letters, usually at the beginning of sentences, and mentions one or more numbers. Five of the uppercase letters form the combination that opens the safe. By combining the digits from all the numbers in the appropriate way you get a numeric target. (The details of constructing the target number are classified.) To find the combination you must select five letters v, w, x, y, and z that satisfy the following equation, where each letter is replaced by its ordinal position in the alphabet (A=1, B=2, ..., Z=26). The combination is then vwxyz. If there is more than one solution then the combination is the one that is lexicographically greatest, i.e., the one that would appear last in a dictionary." 

v - w^2 + x^3 - y^4 + z^5 = target 

"For example, given target 1 and letter set ABCDEFGHIJKL, one possible solution is FIECB, since 6 - 9^2 + 5^3 - 3^4 + 2^5 = 1. There are actually several solutions in this case, and the combination turns out to be LKEBA. Klein thought it was safe to encode the combination within the engraving, because it could take months of effort to try all the possibilities even if you knew the secret. But of course computers didn't exist then." 

=== Op tech directive, computer division, 2002/11/02 12:30 CST === 

"Develop a program to find Klein combinations in preparation for field deployment. Use standard test methodology as per departmental regulations. Input consists of one or more lines containing a positive integer target less than twelve million, a space, then at least five and at most twelve distinct uppercase letters. The last line will contain a target of zero and the letters END; this signals the end of the input. For each line output the Klein combination, break ties with lexicographic order, or 'no solution' if there is no correct combination. Use the exact format shown below."

 

Sample Input

1 ABCDEFGHIJKL11700519 ZAYEXIWOVU3072997 SOUGHT1234567 THEQUICKFROG0 END

 

Sample Output

LKEBAYOXUZGHOSTno solution

 

////  main.cpp//  Safecracker////  Created by wenhan on 2017/9/6.//  Copyright © 2017年 wenhan. All rights reserved./*  给出一个N和一个字符串,这题的意思是指在字符串中取出5个字母组成一个新的串,其中A=1,B=2,C=3......Z=26,使    这5个字母按顺序填入式子中，使式子等于N，如果有多个满足，找出字典数最大的一个，如果没有输出no solution*///  直接在字符串中所有字母从小到大搜索即可#include <iostream>#include <cstdio>#include <cstring>#include <cmath>using namespace std;int a[30],b[30];   //a标记26个字母在字符串中出现的次数,b标记26个字母是否已经出现在那5个字母中char c[6];//记录5个字母bool f;//判断是否已经找到void dfs(int n,int cur,int w,int t){    if(f==true)        return;    if(cur==5)//找到5个    {   if(w==n)       {           f=true;           return;       }    }    else        for(int i=26;i>=1;i--)            if(a[i]&&!b[i])            {                b[i]=1;                w=w+pow(i,cur+1)*t;                c[cur+1]=i+'A'-1;                dfs(n,cur+1,w,-t);                if(f)//注意，要中断                    break;                w=w-pow(i,cur+1)*t;                b[i]=0;            }}int main() {    int n;    string s;    while (cin>>n>>s) {        if(s=="END"&&n==0)            break;        f=false;        memset(a, 0, sizeof(a));        memset(b, 0, sizeof(b));        for(int i=0;i<s.length();i++)            a[s[i]-'A'+1]++;        dfs(n,0,0,1);        if(f)            for(int i=1;i<=5;i++)                printf("%c",c[i]);        else            printf("no solution");        printf("\n");    }    // insert code here...    //std::cout << "Hello, World!\n";    return 0;}