HDU 2665

思路：划分树

#include<iostream>#include<algorithm>#include<cstdio>#define MAX 100005using 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;}