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  • LOJ-6285-数列分块入门9

    链接:

    https://loj.ac/problem/6285

    题意:

    给出一个长为 的数列,以及 个操作,操作涉及询问区间的最小众数。

    思路:

    vector维护每个值的出现位置, 预处理第i快到第j块 的众数,然后对不成块的跑暴力,
    数组开小了一直wa..找题解,好多题解代码也过不了...

    代码:

    #include <iostream>
    #include <cstdio>
    #include <cstring>
    #include <vector>
    //#include <memory.h>
    #include <queue>
    #include <set>
    #include <map>
    #include <algorithm>
    #include <math.h>
    #include <stack>
    #include <string>
    #include <assert.h>
    #include <iomanip>
    #define MINF 0x3f3f3f3f
    using namespace std;
    typedef long long LL;
    const int MAXN = 1e5+10;
    const int MOD = 10007;
    
    int a[MAXN], b[MAXN], Tag[MAXN];
    int Num[MAXN];
    int Dp[2010][2010];
    int Belong[MAXN];
    bool Vis[MAXN];
    vector<int> Number[MAXN];
    int n, part, pos;
    
    inline int read()
    {
        int ret = 0, c, f = 1;
        for(c = getchar(); !(isdigit(c) || c == '-'); c = getchar());
        if(c == '-') f = -1, c = getchar();
        for(; isdigit(c); c = getchar()) ret = ret * 10 + c - '0';
        if(f < 0) ret = -ret;
        return ret;
    }
    
    void Init(int x)
    {
        int MaxNum = 0;
        int Mode = 0;
        memset(Num, 0, sizeof(Num));
        for (int i = (x-1)*part+1;i <= n;i++)
        {
            int p = Belong[i];
            Num[a[i]]++;
            if (Num[a[i]] > MaxNum)
            {
                MaxNum = Num[a[i]];
                Mode = a[i];
            }
            if (Num[a[i]] == MaxNum && Mode > a[i])
                Mode = a[i];
            Dp[x][p] = Mode;
        }
    }
    
    int GetCnt(int l, int r, int v)
    {
    //    int lp = lower_bound(Number[v].begin(), Number[v].end(), l)-Number[v].begin();
    //    int rp = upper_bound(Number[v].begin(), Number[v].end(), r)-Number[v].begin();
    //    return rp-lp+1;
        vector<int>::iterator x = upper_bound(Number[v].begin(), Number[v].end(), r);
        vector<int>::iterator y = lower_bound(Number[v].begin(), Number[v].end(), l);
        return x - y ;
    }
    
    int Query(int l, int r)
    {
        int mode = Dp[Belong[l]+1][Belong[r]-1];
        int MaxNum = GetCnt(l, r, mode);
        memset(Vis, 0, sizeof(Vis));
        Vis[mode] = 1;
        for (int i = l;i <= min(Belong[l]*part, r);i++)
        {
            if (Vis[a[i]])
                continue;
            Vis[a[i]] = 1;
            int cnt = GetCnt(l, r, a[i]);
            if (cnt > MaxNum || (MaxNum == cnt && a[i] < mode))
            {
                MaxNum = cnt;
                mode = a[i];
            }
        }
        if (Belong[l] != Belong[r])
        {
            for (int i = max((Belong[r]-1)*part+1, l);i <= r;i++)
            {
                if (Vis[a[i]])
                    continue;
                Vis[a[i]] = 1;
                int cnt = GetCnt(l, r, a[i]);
                if (cnt > MaxNum || (MaxNum == cnt && a[i] < mode))
                {
                    MaxNum = cnt;
                    mode = a[i];
                }
            }
        }
        return mode;
    }
    
    int main()
    {
    //    scanf("%d", &n);
        n = read();
        part = 80;
        memset(Tag, -1, sizeof(Tag));
        for (int i = 1;i <= n;i++)
        {
    //        scanf("%d", &a[i]);
            a[i] = read();
            b[i] = a[i];
            Belong[i] = (i-1)/part+1;
        }
        sort(b+1, b+1+n);
        pos = unique(b+1, b+1+n)-(b+1);
        for (int i = 1;i <= n;i++)
            a[i] = lower_bound(b+1, b+1+pos, a[i])-b;
    
        for (int i = 1;i <= Belong[n];i++)
            Init(i);
        for (int i = 1;i <= n;i++)
            Number[a[i]].push_back(i);
        int op, l, r, c;
        for (int i = 1;i <= n;i++)
        {
    //        scanf("%d%d", &l, &r);
            l = read(), r = read();
            printf("%d
    ", b[Query(l, r)]);
        }
    
        return 0;
    }
    
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  • 原文地址:https://www.cnblogs.com/YDDDD/p/11434752.html
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