CF962E Byteland, Berland and Disputed Cities

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概述

思路：

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

实现：

 1 #include <bits/stdc++.h>
 2 using namespace std;
 3 typedef long long ll;
 4 const int MAXN = 200005;
 5 int t[MAXN], n;
 6 char c[MAXN];
 7 int get_sum(int i, vector<int> & v, char color)
 8 {
 9     int maxn = 0, last = v[i];
10     for (int j = v[i] + 1; j <= v[i + 1]; j++)
11     {
12         if (c[j] == color || c[j] == 'P')
13         {
14             if (t[j] - t[last] > maxn) maxn = t[j] - t[last];
15             last = j;
16         }
17     }
18     return last == v[i] ? 0 : t[v[i + 1]] - t[v[i]] - maxn;
19 }
20 int main()
21 {
22     while (cin >> n)
23     {
24         int p_start = -1, p_end = -1, r_start = -1, r_end = -1, b_start = -1, b_end = -1;
25         vector<int> v;
26         for (int i = 0; i < n; i++) 
27         { 
28             cin >> t[i] >> c[i];
29             if (c[i] == 'P')
30             {
31                 p_end = i;
32                 if (p_start == -1) p_start = i;
33                 v.push_back(i);
34             }
35             else if (c[i] == 'R')
36             {
37                 r_end = i;
38                 if (r_start == -1) r_start = i;
39             }
40             else
41             {
42                 b_end = i;
43                 if (b_start == -1) b_start = i;
44             }
45         }
46         ll ans = 0;
47         if (p_start == -1) 
48         { 
49             if (r_start != -1) ans += t[r_end] - t[r_start];
50             if (b_start != -1) ans += t[b_end] - t[b_start];
51             cout << ans << endl;
52             continue;
53         }
54         if (r_start != -1)
55         {
56             if (r_start < p_start) ans += t[p_start] - t[r_start];
57             if (r_end > p_end) ans += t[r_end] - t[p_end];
58         }
59         if (b_start != -1)
60         {
61             if (b_start < p_start) ans += t[p_start] - t[b_start];
62             if (b_end > p_end) ans += t[b_end] - t[p_end];
63         }
64         for (int i = 0; i < v.size() - 1; i++)
65         {
66             int tmp_R = get_sum(i, v, 'R'), tmp_B = get_sum(i, v, 'B');
67             if (!tmp_R && !tmp_B) { ans += t[v[i + 1]] - t[v[i]]; continue; }
68             int minn = 2 * (t[v[i + 1]] - t[v[i]]);
69             int tmp = tmp_R + tmp_B + t[v[i + 1]] - t[v[i]];
70             minn = min(minn, tmp);
71             ans += minn;
72         }
73         cout << ans << endl;
74     }
75     return 0;
76 }