HDU2852 KiKi's K-Number

Posted 2020-08-10

题解:

树状求第k大数题目。。二分就行。。。

不过感觉二分是玄学。。。要多试几个不同的二分方式。。。。

代码:

#include<iostream>
#include<cstring>
#include<cstdio>
#include<algorithm>
#include<map>
#include<set>
using namespace std;
using namespace std;
#define pb push_back
#define mp make_pair
#define se second
#define fs first
#define ll long long
#define CLR(x) memset(x,0,sizeof x)
#define SZ(x) ((int)(x).size())
#define FOR(it,c) for(__typeof((c).begin()) it=(c).begin();it!=(c).end();it++)
typedef pair<int,int> P;
const double eps=1e-9;
const int maxn=100010;
const int N=1000+10;
const int mod=9901;

ll read()
{
    ll x=0,f=1;char ch=getchar();
    while(ch<‘0‘||ch>‘9‘){if(ch==‘-‘)f=-1;ch=getchar();}
    while(ch>=‘0‘&&ch<=‘9‘){x=x*10+ch-‘0‘;ch=getchar();}
    return x*f;
}
//-----------------------------------------------------------------------------

int m,op,a,b;
int c[maxn];

int lowbit(int x){return x&-x;}

void add(int x,int v){
    while(x<maxn){
        c[x]+=v;
        x+=lowbit(x);
    }
}

int sum(int x){
    int cnt=0;
    while(x){
        cnt+=c[x];
        x-=lowbit(x);
    }
    return cnt;
}

int bs(int l,int r,int goal){
    int tmp=-1;
    int m,L=l,R=r;
    while(L<R){
        m=(L+R)>>1;
        if(sum(m)-sum(l-1)>=goal){
            tmp=m;
            R=m;
        }
        else L=m+1;
    }
    return tmp;
}


int main(){
    while(~scanf("%d",&m)){
        CLR(c);
        for(int i=1;i<=m;i++){
            scanf("%d",&op);
            if(op==0){
               scanf("%d",&a);
               add(a,1);    
            }
            if(op==1){
                scanf("%d",&b);
                if(sum(b)-sum(b-1)==0) printf("No Elment!\n");
                else add(b,-1);
            }
            if(op==2){
                scanf("%d%d",&a,&b);
                if(bs(a+1,maxn,b)==-1) printf("Not Find!\n");
                else printf("%d\n",bs(a+1,maxn,b));    
            }
        }
    }
    return 0;
}