主席树【模板】

                              求区间第k小
 今天打多校,找了好几个板子改,还是败了,就用队友这个吧!!

/*
    求区间第k小,相应的,第k大也行(主席树)
     
*/
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#define INF 0x3f3f3f3f
#define eps 1e-8
#define ll long long
using namespace std;

const int MAXN = 200005;
const int MAXM = 4000005; //  maxn的20倍
int a[MAXN];
int tot;
vector v;
struct Tree
{
    int count;
    int left, right;
};

int root[MAXN];
Tree node[MAXM];

int null;

int newnode(int count, int left, int right)
{
    node[tot].count=count;
    node[tot].left=left;
    node[tot].right=right;
    return tot++;
}

int inn(int rt, int l, int r, int k)
{
    if (l <= k && k <= r)
    {
        if (l == r)
        {
            return newnode(node[rt].count + 1, 0, 0);
        }
        int m = (l + r) >> 1;
        return newnode(node[rt].count + 1, inn(node[rt].left, l, m, k),  inn(node[rt].right, m + 1, r, k));
    }
    return rt;
}

int query(int p, int q, int l, int r, int k)
{
    if (l == r)
    {
        return v[l];
    }
    int m = (l + r) >> 1;
    int cot = node[node[q].left].count - node[node[p].left].count;
    if (cot >= k)
    {
        return query(node[p].left, node[q].left, l, m, k);
    }
    return query(node[p].right, node[q].right, m + 1, r, k - cot);
}

int main()
{
    int n, q;
    while(scanf("%d%d", &n, &q) == 2)
    {
        v.clear();
        tot = 0;
        for(int i = 1; i <= n; i ++)
        {
            scanf("%d", &a[i]);
            v.push_back(a[i]);
        }
        sort(v.begin(), v.end());
        v.erase(unique(v.begin(), v.end()), v.end());
        int m = v.size();
        null = newnode(0, 0, 0);
        root[0] = newnode(0, 0, 0);
        for(int i = 1; i <= n; i ++)
        {
            a[i] = lower_bound(v.begin(), v.end(), a[i]) - v.begin();
            root[i] = inn(root[i - 1], 0, m - 1, a[i]);
        }
        while(q--)
        {
            int l, r, k;
            scanf("%d%d%d", &l, &r,&k);
            int pos=query(root[l - 1], root[r], 0, m - 1,k);
            printf("%d\n",pos);

        }
    }
    return 0;
}

 

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