【Bzoj1901】Dynamic Ranking

題意

給一個序列，每次詢問[l,r]區間內第k小的數字。帶修改。

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解析

同2B平衡樹的操作。
操作少可以打得簡單一點。

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#include <cstdio>
#include <algorithm>

#define Rep( i , _begin , _end ) for(int i=(_begin),i##_END=(_end);i<=(i##_END);i++)
#define For( i , _begin , _end ) for(int i=(_begin),i##_END=(_end);i!=(i##_END);i++)
#define Lop( i , _begin , _end ) for(int i=(_begin),i##_END=(_end);i>=(i##_END);i++)
#define Dnt( i , _begin , _end ) for(int i=(_begin),i##_END=(_end);i!=(i##_END);i++)

using std :: max;
using std :: min;

const int maxx = (10000 << 2) + 25;
const int maxm = 10000 * 4 * 16 + 25;
const int Inf = 1000000000;

int n,m,x,y,z,k,num,ans,f;
int ch[maxm][2],fix[maxm],v[maxm],size[maxm],cnt[maxm];
int rt[maxx],a[maxx];

char s[10];

namespace Treap{

    int chk(int x,int y) {return x == y? 20011025 : x > y;}

    void upt(int i) {size[i] = size[ch[i][0]] + size[ch[i][1]] + cnt[i];}

    void rotate(int &i,int f){
        int t = ch[i][f];
        ch[i][f] = ch[t][f^1];
        ch[t][f^1] = i;
        size[t] = size[i];
        upt(i);i = t;
    }

    void insert(int &i,int x){
        if(!i) {v[i=++num] = x;size[i] = cnt[i] = 1;fix[i] = rand();return;}
        size[i] ++;
        if(v[i] == x) {cnt[i] ++;return;}
        int tmp = chk(x,v[i]);
        insert(ch[i][tmp],x);
        if(fix[ch[i][tmp]] < fix[i]) rotate(i,tmp);
    }

    void remove(int &i,int x){
        if(!i) return;
        int tmp = chk(x,v[i]);
        if(x != v[i]) size[i] --,remove(ch[i][tmp],x);
        if(x == v[i]){
            if(cnt[i] > 1) {cnt[i] --;size[i] --;return;}
            if(ch[i][0] * ch[i][1] == 0) {i = ch[i][0] + ch[i][1];return;}
            tmp = chk(fix[ch[i][0]],fix[ch[i][1]]);
            rotate(i,tmp);remove(i,x);
        }
    }

    int Dfs(int i,int x){
        if(v[i] == x) return cnt[i];
        if(!i) return 0;
        return x < v[i]? Dfs(ch[i][0],x) : Dfs(ch[i][1],x);
    }

    int Qrank(int i,int x){
        if(!i) return 0;
        if(v[i] == x) return size[ch[i][0]];
        else return x <= v[i]? Qrank(ch[i][0],x) : cnt[i] + size[ch[i][0]] + Qrank(ch[i][1],x);
    }

}

namespace Segment_Tree{

    using namespace Treap;

    void Build(int t,int l,int r){
        Rep( i , l , r ) insert(rt[t],a[i]);
        if(l == r) return;int mid = (l+r) >> 1;
        Build(t<<1,l,mid);Build(t<<1|1,mid+1,r);
    }

    void modify(int i,int pos,int l,int r,int k){
        remove(rt[i],a[pos]);
        insert(rt[i],k);
        if(l == r) return;int mid = (l+r) >> 1;
        if(pos <= mid) modify(i<<1,pos,l,mid,k);
        if(pos >  mid) modify(i<<1|1,pos,mid+1,r,k);
    }

    int Query(int i,int x,int y,int l,int r,int k){
        if(x <= l && r <= y) return Qrank(rt[i],k);
        int mid = (l+r) >> 1;int ans = 0;
        if(x <= mid) ans += Query(i<<1,x,y,l,mid,k);
        if(y >  mid) ans += Query(i<<1|1,x,y,mid+1,r,k);
        return ans; 
    }

    int Ex_Order(int x,int y,int k){
        int l = 0,r = Inf,ans;
        while(l <= r){
            int mid = (l+r) >> 1;
            if(Query(1,x,y,1,n,mid) + 1 <= k) ans = mid,l = mid + 1;
            else r = mid - 1;
        }
        return ans;
    }

}

namespace Bit{

    using namespace Treap;

    void Add(int x,int k,int f){
        for(int i=x;i<=n;i+=i&(-i))
            f? insert(rt[i],k) : remove(rt[i],k);
    }

    int Query_B(int x,int k){
        int ans = 0;
        for(int i=x;i;i-=i&(-i))
            ans += Qrank(rt[i],k);
        return ans;
    }

    int Ex_Order_B(int x,int y,int k){
        int l = 0,r = Inf,ans;
        while(l <= r){
            int mid = (l+r) >> 1;
            if(Query_B(y,mid) - Query_B(x-1,mid) + 1 <= k) ans = mid,l = mid + 1;
            else r = mid - 1;
        }
        return ans;
    }

}

using namespace Segment_Tree;
using namespace Bit;

int main(){
    scanf("%d%d",&n,&m);
    Rep( i , 1 , n ) scanf("%d",&a[i]);
    Rep( i , 1 , n ) Add(i,a[i],1);
    while( m-- ){
        scanf("%s",s);
        if(s[0] == 'C') scanf("%d%d",&x,&y),Add(x,a[x],0),Add(x,y,1),a[x] = y;
        if(s[0] == 'Q') scanf("%d%d%d",&x,&y,&z),printf("%d\n",Ex_Order_B(x,y,z));
    }
    return 0;
}