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;
}