poj 2104 K-th Number (静态区间第k大，主席树)

来源：互联网发布：中英文转换器软件编辑：程序博客网时间：2024/05/20 00:11
查询区间第K大，而且没有修改。
使用划分树是可以做的。
#include <set>#include <map>#include <stack>#include <queue>#include <deque>#include <cmath>#include <vector>#include <string>#include <cstdio>#include <cstdlib>#include <cstring>#include <iostream>#include <algorithm>using namespace std;#define L(i) i<<1#define R(i) i<<1|1#define INF  0x3f3f3f3f#define pi acos(-1.0)#define eps 1e-9#define maxn 100100#define MOD 1000000007const int MAXN = 100010;const int M = MAXN * 30;int n,q,m,tot;int a[MAXN], t[MAXN];int T[M], lson[M], rson[M], c[M];void Init_hash(){    for(int i = 1; i <= n;i++)        t[i] = a[i];    sort(t+1,t+1+n);    m = unique(t+1,t+1+n)-t-1;}int build(int l,int r){    int root = tot++;    c[root] = 0;    if(l != r)    {        int mid = (l+r)>>1;        lson[root] = build(l,mid);        rson[root] = build(mid+1,r);    }    return root;}int hash(int x){    return lower_bound(t+1,t+1+m,x) - t;}int update(int root,int pos,int val){    int newroot = tot++, tmp = newroot;    c[newroot] = c[root] + val;    int l = 1, r = m;    while(l < r)    {        int mid = (l+r)>>1;        if(pos <= mid)        {            lson[newroot] = tot++; rson[newroot] = rson[root];            newroot = lson[newroot]; root = lson[root];            r = mid;        }        else        {            rson[newroot] = tot++; lson[newroot] = lson[root];            newroot = rson[newroot]; root = rson[root];            l = mid+1;        }        c[newroot] = c[root] + val;    }    return tmp;}int query(int left_root,int right_root,int k){    int l = 1, r = m;    while( l < r)    {        int mid = (l+r)>>1;        //printf("%d %d %d %d %d\n",l,r,left_root,right_root,k);        if(c[lson[left_root]]-c[lson[right_root]] >= k )        {            r = mid;            left_root = lson[left_root];            right_root = lson[right_root];        }        else        {            l = mid + 1;            k -= c[lson[left_root]] - c[lson[right_root]];            left_root = rson[left_root];            right_root = rson[right_root];        }    }    return l;}int main(){    //freopen("in.txt","r",stdin);    //freopen("out.txt","w",stdout);    while(scanf("%d%d",&n,&q) == 2)    {        tot = 0;        for(int i = 1;i <= n;i++)            scanf("%d",&a[i]);        Init_hash();        T[n+1] = build(1,m);        for(int i = n; i ;i--)        {            int pos = hash(a[i]);            T[i] = update(T[i+1],pos,1);        }        while(q--)        {            int l,r,k;            scanf("%d%d%d",&l,&r,&k);            printf("%d\n",t[query(T[l],T[r+1],k)]);        }    }    return 0;}
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