poj 2104 K-th Number

静态区间第k大，裸的主席树

直接上代码吧

#include<algorithm>
#include<cstdio>
using namespace std;

const int INF = 0x3f3f3f3f;
struct node{
    int v;
    int l,r;
    void init(){
        v = 0;
        l = r = -1;
    }
};

const int maxn = 112345;
const int maxlog = 20;

node arr[maxn*maxlog];
int head[maxn];

int _cnt;

int newnode(){
    arr[_cnt].init();
    return _cnt++;
}

int newtree(int l,int r){
    int ret = newnode();
    if(l == r){
        return ret;
    }
    int m = (l + r)/2;
    arr[ret].l = newtree(l,m);
    arr[ret].r = newtree(m+1,r);
    return ret;
}

int buildtree(int bef,int l,int r,int v){
    int ret = newnode();
    arr[ret] = arr[bef];
    arr[ret].v++;
    if(l == r){
        return ret;
    }
    int m = (l+r) / 2;
    if(v <= m) arr[ret].l = buildtree(arr[bef].l,l  ,m,v);
    else       arr[ret].r = buildtree(arr[bef].r,m+1,r,v);
    return ret;
}


int val[maxn];

void init(int n,int siz){
    _cnt = 0;
    head[0] = newtree(1,siz);
    for(int i = 1;i<=n;i++){
         head[i] = buildtree(head[i-1],1,siz,val[i]);
    }
}


int req(int bef,int aft,int l,int r,int k){
    if(l == r){
        return l;
    }
    int siz = arr[arr[aft].l].v - arr[arr[bef].l].v;
    int m = (l+r)/2;
    if(k <= siz){
        return req(arr[bef].l,arr[aft].l,l,m,k);
    }
    else{
        return req(arr[bef].r,arr[aft].r,m+1,r,k-siz);
    }
}

int msp[maxn],mlen;

int query(int l,int r,int k,int siz){
    return msp[req(head[l-1],head[r],1,siz,k)];
}


int main(){
    int T;
    scanf("%d",&T);
    int n,m;
    while(T-- && ~scanf("%d %d",&n,&m)){
        mlen = 0;
        for(int i=1;i<=n;i++){
            scanf("%d",&val[i]);
            msp[mlen++] = val[i];
        }
        msp[mlen++] = -INF;
        sort(msp,msp+mlen);
        mlen = unique(msp,msp+mlen) - msp;
        for(int i=1;i<=n;i++){
            val[i] = lower_bound(msp,msp+mlen,val[i]) - msp;
        }
        init(n,mlen);
        int l,r,k;
        while(m--){
            scanf("%d %d %d",&l,&r,&k);
            printf("%d\n",query(l,r,k,mlen));
        }
    }
    return 0;
}

1A真是太爽啦~