CodeForces 830B - Cards Sorting

Posted 2020-09-28 nicetomeetu

将每个数字的位置存进该数字的vector中

原数组排个序从小到大处理，每次在vector里二分找到距离当前位置“最远”的位置（相差最大），更新答案

树状数组维护每个数字现在的位置和原位置之差

 1 #include <bits/stdc++.h>
 2 using namespace std;
 3 #define LL long long
 4 const int N = 100005;
 5 int n;
 6 int a[N], b[N];
 7 vector<int> v[N];
 8 int c[N];
 9 void modify(int x, int num)
10 {
11     while (x <= 100000) c[x] += num, x += x&-x;
12 }
13 int sum(int x)
14 {
15     int s = 0;
16     while (x) s += c[x], x -= x&-x;
17     return s;
18 }
19 int main()
20 {
21     scanf("%d", &n);
22     for (int i = 1; i <= n; i++) scanf("%d", &a[i]), b[i] = a[i];
23     sort(b+1, b+1+n);
24     for (int i = 1; i <= n; i++)
25         v[a[i]].push_back(i);
26     LL ans = 0;
27     int now = 0;
28     for (int i = 1; i <= n;)
29     {
30         int p = lower_bound(v[b[i]].begin(), v[b[i]].end(), now) - v[b[i]].begin();
31         if (p == 0)
32         {
33             int pos = v[b[i]][v[b[i]].size()-1];
34             ans += pos - sum(pos) - (now - sum(now));
35             now = pos;
36         }
37         else
38         {
39             int pos = v[b[i]][p-1];
40             ans += n - sum(n) - (now-sum(now)) + pos - sum(pos);
41             now = pos;
42         }
43         for (int j = 0; j < v[b[i]].size(); j++) modify(v[b[i]][j], 1);
44         i += v[b[i]].size();
45     }
46     cout << ans << endl;
47 }