poj 2352 & Ural 1028 数星星 题解

Posted 2022-08-30 donkey2603089141

一道水题，由于x坐标递增y坐标也递增于是前缀和统计即可，用树状数组实现。

#include<bits/stdc++.h>
using namespace std;
const int maxn=15010;
const int maxx=32010;
inline long long read()
    long long 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<<1)+(x<<3)+(ch^48);
        ch=getchar();
    
    return x*f;

long long n,c[maxx],ans[maxn];
long long lowbit(long long x)
    return x&(-x);

void add(long long x)
    for(x;x<=maxx;x+=lowbit(x)) c[x]+=1;

long long ask(long long x)
    long long tmp=0;
    for(;x;x-=lowbit(x)) tmp+=c[x];
    return tmp;

int main()
    n=read();
    for(long long i=1;i<=n;++i)
        long long x,y;
        x=read();y=read();
        long long s=ask(x+1);
        add(x+1);
        ans[s]++;
    
    for(long long i=0;i<n;++i)
        printf("%lld\n",ans[i]);
    
    
    return 0;

/*
5 
1 1
5 1
7 1
3 3
5 5
*/