小米OJ 有多少个等差数列

题目链接 https://code.mi.com/problem/list/view?id=20

代码

 #include <bits/stdc++.h>

 using namespace std;

 int cnt = ;

 void getNumVec(vector<int>& v, string s)
 {
     int temp = , flag = ;
     for (int i = ;i < s.length(); ++i)
     {
         if (s[i] == ' ')
         {
             v.push_back(temp * flag);
             temp = ;
             flag = ;
         }
         else if (s[i] == '-')
         {
             flag = -;
         }
         else
         {
             temp *= ;
             temp += s[i] - '';
         }
     }
     v.push_back(temp * flag);
 }

 bool check(vector<int> v)
 {
     int sz = v.size();
     if (sz < )
     {
         return false;
     }

     if (sz == )
     {
         return true;
     }

     int d = v[] - v[];
     for (int i = ; i < sz; ++i)
     {
         if (v[i] - v[i - ] != d)
         {
             return false;
         }
     }
     return true;
 }

 void dfs(vector<int>& v, vector<int>& temp, int start, int sz)
 {
     bool flag = false;
     for (int i = start;i < sz; ++i)
     {
         temp.push_back(v[i]);
         flag = check(temp);
         if (flag || temp.size() < ) //剪枝
         {
             if (flag)
             {
                 ++cnt;
             }
             dfs(v, temp, i + , sz);
         }
         temp.pop_back();
     }
 }

 int main()
 {
     string s;
     getline(cin, s);

     vector<int> v, temp;
     getNumVec(v, s);
     int sz = v.size();
     dfs(v, temp, , sz);

     cout << cnt << endl;

     return ;
 }