HDU 2665 Kth number 主席树模板题

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题目链接: http://acm.hdu.edu.cn/showproblem.php?pid=2665

主席树模板题

代码 :

#include <iostream>#include <cstdio>#include <cstring>#include <algorithm>#define sf scanf#define pf printf#define totNode maxn * 60using namespace std;const int maxn = 100000 + 50;int ch[totNode][2],SUM[totNode],tot;void Insert(int prt,int rt,int l,int r,int x,int v){    SUM[rt] = SUM[prt] + v;    while(l < r){        int mid = l + r >> 1;        if(x <= mid){            ch[rt][0] = tot++;            ch[rt][1] = ch[prt][1];            rt = ch[rt][0],prt = ch[prt][0];            r = mid;        }        else{            ch[rt][1] = tot++;            ch[rt][0] = ch[prt][0];            rt = ch[rt][1],prt = ch[prt][1];            l = mid + 1;        }        SUM[rt] = SUM[prt] + v;    }}int Query(int rt1,int rt2,int l,int r,int k){    while(l < r){        int mid = l + r >> 1;        if( (SUM[ch[rt2][0]] - SUM[ch[rt1][0]]) >= k){            r = mid;            rt1 = ch[rt1][0],rt2 = ch[rt2][0];        }        else{            k = k - (SUM[ch[rt2][0]] - SUM[ch[rt1][0]]);            l = mid + 1;            rt1 = ch[rt1][1],rt2 = ch[rt2][1];        }    }    return l;}int rts[maxn];struct Node{    int v,id;}Nodes[maxn];bool cmp(const Node& a,const Node& b){    return a.v < b.v;}int pos[maxn];int main(){    int n,m;    int T;sf("%d",&T);    while(T--){        sf("%d %d",&n,&m);        tot = 1;        SUM[0] = 0;ch[0][0] = ch[0][1] = 0;        for(int i = 1;i <= n;++i){            sf("%d",&Nodes[i].v);Nodes[i].id = i;        }        sort(Nodes + 1,Nodes + 1 + n,cmp);        for(int i = 1;i <= n;++i){            pos[Nodes[i].id] = i;        }        for(int i = 1;i <= n;++i) Insert(rts[i - 1],rts[i] = tot++,1,n,pos[i],1);        while(m--){            int x,y,k;sf("%d %d %d",&x,&y,&k);            pf("%d\n",Nodes[Query(rts[x - 1],rts[y],1,n,k)].v);        }    }}

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