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 = 200005;

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 = 1; i <= n; ++i)
    {
        scanf("%d", num + i);
        if (num[i] > n)
            num[i] = n;
    }
    
    for (int i = 0; i <= n; ++i)
        lst[i] = n + 1;
    
    for (int i = n; i >= 1; --i)
        nxt[i] = lst[num[i]], lst[num[i]] = i;
        
    for (int i = 1; i <= n; ++i)
    {
        mex[i] = mex[i - 1];
        vis[num[i]] = true;
        while (vis[mex[i]])
            ++mex[i];
    }
    
    for (int i = 1; i <= m; ++i)
        scanf("%d%d", &q[i].l, &q[i].r), q[i].t = i;
    
    std::sort(q + 1, q + m + 1, cmp);
    
    int left = 1;
    
    for (int i = 1; i <= m; ++i)
    {
        while (left < q[i].l)
        {
            int t = nxt[left];
            int p = num[left];
            for (int j = t - 1; j > left; --j)
            {
                if (mex[j] <= p)break;
                else mex[j] = p;
            }
            ++left;
        }
        
        ans[q[i].t] = mex[q[i].r];
    }
    
    for (int i = 1; i <= m; ++i)
        printf("%d
", ans[i]);
}

@Author: YouSiki