HDU 2665

思路：划分树

#include<iostream>
#include<algorithm>
#include<cstdio>
#define MAX 100005
using namespace std;
class TreeNode
{
    public:
        int left, right, mid;
};
TreeNode node[4*MAX];
int val[30][MAX];
int ToLeft[30][MAX];
int sorted[MAX];
void BuildTree(int k, int d, int l, int r)
{
    node[k].left = l;
    node[k].right = r;
    node[k].mid = (l + r) >> 1;
    if(l == r)
        return ;
    int mid = (l + r) >> 1;
    int lsame = mid - l + 1;
    for(int i = l;i <= r;i ++)
    {
        if(val[d][i] < sorted[mid])
            lsame --;
    }
    int lpos = l;
    int rpos = mid + 1;
    for(int i = l;i <= r;i ++)
    {
        if(i == l)
            ToLeft[d][i] = 0;
        else
            ToLeft[d][i] = ToLeft[d][i-1];
        if(val[d][i] < sorted[mid])
        {
            ToLeft[d][i] ++;
            val[d+1][lpos ++] = val[d][i];
        }
        else if(val[d][i] > sorted[mid])
        {
            val[d+1][rpos ++] = val[d][i];
        }
        else
        {
            if(lsame)
            {
                ToLeft[d][i] ++;
                val[d+1][lpos ++] = val[d][i];
                lsame --;
            }
            else
                val[d+1][rpos ++] = val[d][i];
        }
    }
    BuildTree(k << 1, d+1, l, mid);
    BuildTree(k << 1|1, d+1, mid + 1, r);
}

int Query(int l, int r, int k, int d, int idx)
{
    if(l == r)
        return val[d][l];
    int s;
    int ss;
    if(l == node[idx].left)
    {
        s = ToLeft[d][r];
        ss = 0;
    }
    else
    {
        s = ToLeft[d][r] - ToLeft[d][l-1];
        ss = ToLeft[d][l-1];
    }
    if(s >= k)
    {
        int newl = node[idx].left + ss;
        int newr = node[idx].left + ss + s - 1;
        return Query(newl, newr, k, d + 1, idx << 1);
    }
    else
    {
        int mid = node[idx].mid;
        int b = r - l - s + 1;
        int bb = l - node[idx].left - ss;
        int newl = mid + bb + 1;
        int newr = mid + bb + b;
        return Query(newl, newr, k - s, d + 1,  idx << 1|1);
    }
}

int main(int argc, char const *argv[])
{
    int c, n, m, l, r, k;
    //freopen("in.c", "r", stdin);
    scanf("%d", &c);
    while(c--)
    {
        scanf("%d%d", &n, &m);
        for(int i = 1;i <= n;i ++)
        {
            scanf("%d", &val[0][i]);
            sorted[i] = val[0][i];
        }
        sort(sorted + 1, sorted + n + 1);
        BuildTree(1, 0, 1, n);
        for(int i = 0; i< m;i ++)
        {
            scanf("%d%d%d", &l, &r, &k);
            printf("%d\n", Query(l, r, k, 0, 1));
        }
    }
    return 0;
}