PAT甲级——A1038 Recover the Smallest Number

Given a collection of number segments, you are supposed to recover the smallest number from them. For example, given { 32, 321, 3214, 0229, 87 }, we can recover many numbers such like 32-321-3214-0229-87 or 0229-32-87-321-3214 with respect to different orders of combinations of these segments, and the smallest number is 0229-321-3214-32-87.

Input Specification:

Each input file contains one test case. Each case gives a positive integer N (≤) followed by N number segments. Each segment contains a non-negative integer of no more than 8 digits. All the numbers in a line are separated by a space.

Output Specification:

For each test case, print the smallest number in one line. Notice that the first digit must not be zero.

Sample Input:

5 32 321 3214 0229 87

Sample Output:

22932132143287

 #include <iostream>
 #include <string>
 #include <vector>
 #include <algorithm>
 using namespace std;
 //排序问题
 int N;
 vector<string>v, temp;
 string res = "", str = "";
 void permuteDFS(int u,vector<bool>&visit)//使用DFS
 {
     if (u == v.size())
     {
         for (auto a : temp)
             str += a;
         res = res > str ? str : res;
         str = "";
         return;
     }
     for (int i = ; i < N; ++i)
     {
         if (visit[i] == true)continue;
         visit[i] = true;
         temp.push_back(v[i]);
         permuteDFS(i + , visit);
         temp.pop_back();
         visit[i] = false;
     }
 }

 void permutex(int u)//使用递归
 {
     if (u == v.size())
     {
         for (auto a : v)
             str += a;
         res = res > str ? str : res;
         str = "";
     }
     for (int i = u; i < N; ++i)
     {
         swap(v[i], v[u]);
         permutex(i + );
         swap(v[i], v[u]);
     }
 }

 void Sort()//使用排序法则
 {
     sort(v.begin(), v.end(), [](string a, string b) {return a + b < b + a; });
     res = "";
     for (auto a : v)
         res += a;
 }

 int main()
 {
     cin >> N;
     v.resize(N);
     vector<bool>visit(N, false);
     for (int i = ; i < N; ++i)
     {
         cin >> v[i];
         res += v[i];
     }
     //permutex(0);
     //permuteDFS(0, visit);
     Sort();
     while (!res.empty() && res[] == '')
         res.erase(, );
     if (res.size() == )cout << ;
     cout << res << endl;
     return ;
 }