POJ3067 Japan

Posted 2020-08-09

题解:

将一边排序过后就是裸的逆序题了

这里有2种方法

1.add()往下更新,sum()往上更新 求逆序sum(a+1);

2.add)往上更新,sum()往下更新 求逆序sum(maxn)-sum(a);

代码:

1.

#include<iostream>
#include<cstring>
#include<cstdio>
#include<algorithm>
#include<map>
#include<set>
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 lson l,m,rt<<1
#define rson m+1,r,rt<<1|1 
typedef pair<int,int> P;
const double eps=1e-9;
const int maxn=20100;
const int N=110;
const int mod=1e9+7;
const int INF=1e9;

int T,n,m,k;
LL c[maxn];
P p[maxn*100];

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

void add(int x){
    while(x){
        c[x]++;
        x-=lowbit(x);
    }
}

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


int main(){
    int Case=1;
    scanf("%d",&T);
    while(T--){
        CLR(c);
        scanf("%d%d%d",&n,&m,&k);
        for(int i=1;i<=k;i++) scanf("%d%d",&p[i].fs,&p[i].se);
        sort(p+1,p+k+1);
        LL Sum=0;
        for(int i=1;i<=k;i++){
            Sum+=sum(p[i].se+1);
            //cout<<Sum<<endl;
            add(p[i].se);
        }
        printf("Test case %d: %lld\n",Case++,Sum);
    }
    return 0;
}

 

2.

#include<iostream>
#include<cstring>
#include<cstdio>
#include<algorithm>
#include<map>
#include<set>
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 lson l,m,rt<<1
#define rson m+1,r,rt<<1|1 
typedef pair<int,int> P;
const double eps=1e-9;
const int maxn=20100;
const int N=110;
const int mod=1e9+7;
const int INF=1e9;

int T,n,m,k;
LL c[maxn];
P p[maxn*100];

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

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

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


int main(){
    int Case=1;
    scanf("%d",&T);
    while(T--){
        CLR(c);
        scanf("%d%d%d",&n,&m,&k);
        for(int i=1;i<=k;i++) scanf("%d%d",&p[i].fs,&p[i].se);
        sort(p+1,p+k+1);
        LL Sum=0;
        for(int i=1;i<=k;i++){
            Sum+=sum(maxn)-sum(p[i].se);
            //cout<<Sum<<endl;
            add(p[i].se);
        }
        printf("Test case %d: %lld\n",Case++,Sum);
    }
    return 0;
}