BZOJ 3339: Rmq Problem

3339: Rmq Problem

Time Limit: 20 Sec  Memory Limit: 128 MB
Submit: 1075  Solved: 549
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Description

Input

Output

Sample Input

7 5
0 2 1 0 1 3 2
1 3
2 3
1 4
3 6
2 7

Sample Output

3
0
3
2
4

HINT

Source

By Xhr

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和 3585 mex 一模一样，代码不变，AC依旧。

 #include <bits/stdc++.h>
 
 const int mxn = ;
 
 int n, m, num[mxn], nxt[mxn], lst[mxn], mex[mxn], vis[mxn], ans[mxn];
 
 struct query {
     int l, r, t;
 }q[mxn];
 
 inline bool cmp(const query &a, const query &b)
 {
     return a.l < b.l;
 }
 
 signed main(void)
 {
     scanf("%d%d", &n, &m);
 
     for (int i = ; i <= n; ++i)
     {
         scanf("%d", num + i);
         if (num[i] > n)
             num[i] = n;
     }
 
     for (int i = ; i <= n; ++i)
         lst[i] = n + ;
 
     for (int i = n; i >= ; --i)
         nxt[i] = lst[num[i]], lst[num[i]] = i;
 
     for (int i = ; i <= n; ++i)
     {
         mex[i] = mex[i - ];
         vis[num[i]] = true;
         while (vis[mex[i]])
             ++mex[i];
     }
 
     for (int i = ; i <= m; ++i)
         scanf("%d%d", &q[i].l, &q[i].r), q[i].t = i;
 
     std::sort(q + , q + m + , cmp);
 
     int left = ;
 
     for (int i = ; i <= m; ++i)
     {
         while (left < q[i].l)
         {
             int t = nxt[left];
             int p = num[left];
             for (int j = t - ; j > left; --j)
             {
                 if (mex[j] <= p)break;
                 else mex[j] = p;
             }
             ++left;
         }
 
         ans[q[i].t] = mex[q[i].r];
     }
 
     for (int i = ; i <= m; ++i)
         printf("%d\n", ans[i]);
 }

@Author: YouSiki