CF962E Byteland, Berland and Disputed Cities

思路：

http://codeforces.com/blog/entry/58869。

实现：

 #include <bits/stdc++.h>
 using namespace std;
 typedef long long ll;
 const int MAXN = ;
 int t[MAXN], n;
 char c[MAXN];
 int get_sum(int i, vector<int> & v, char color)
 {
     int maxn = , last = v[i];
     for (int j = v[i] + ; j <= v[i + ]; j++)
     {
         if (c[j] == color || c[j] == 'P')
         {
             if (t[j] - t[last] > maxn) maxn = t[j] - t[last];
             last = j;
         }
     }
     return last == v[i] ?  : t[v[i + ]] - t[v[i]] - maxn;
 }
 int main()
 {
     while (cin >> n)
     {
         int p_start = -, p_end = -, r_start = -, r_end = -, b_start = -, b_end = -;
         vector<int> v;
         for (int i = ; i < n; i++)
         {
             cin >> t[i] >> c[i];
             if (c[i] == 'P')
             {
                 p_end = i;
                 if (p_start == -) p_start = i;
                 v.push_back(i);
             }
             else if (c[i] == 'R')
             {
                 r_end = i;
                 if (r_start == -) r_start = i;
             }
             else
             {
                 b_end = i;
                 if (b_start == -) b_start = i;
             }
         }
         ll ans = ;
         if (p_start == -)
         {
             if (r_start != -) ans += t[r_end] - t[r_start];
             if (b_start != -) ans += t[b_end] - t[b_start];
             cout << ans << endl;
             continue;
         }
         if (r_start != -)
         {
             if (r_start < p_start) ans += t[p_start] - t[r_start];
             if (r_end > p_end) ans += t[r_end] - t[p_end];
         }
         if (b_start != -)
         {
             if (b_start < p_start) ans += t[p_start] - t[b_start];
             if (b_end > p_end) ans += t[b_end] - t[p_end];
         }
         for (int i = ; i < v.size() - ; i++)
         {
             int tmp_R = get_sum(i, v, 'R'), tmp_B = get_sum(i, v, 'B');
             if (!tmp_R && !tmp_B) { ans += t[v[i + ]] - t[v[i]]; continue; }
             int minn =  * (t[v[i + ]] - t[v[i]]);
             int tmp = tmp_R + tmp_B + t[v[i + ]] - t[v[i]];
             minn = min(minn, tmp);
             ans += minn;
         }
         cout << ans << endl;
     }
     return ;
 }