排序合集

2299 -- Ultra-QuickSort (poj.org)

#include<iostream>//归并排序 
#include<cstring>
using namespace std;
typedef long long ll;
const int N=500010;
int a[N],tmp[N],ans;
void merge_(ll l,ll mid,ll r){
    int i=l,j=mid+1,t=0;
    while(i<=mid&&j<=r){
        if(a[i]>a[j]){
            tmp[t++]=a[j++];
            ans+=mid-i+1;
        }else tmp[t++]=a[i++];
    }
    while(i<=mid) tmp[t++]=a[i++];
    while(j<=r) tmp[t++]=a[j++];
    for(int i=0;i<t;i++) a[l+i]=tmp[i];
}
void mergesort(ll l,ll r){
    if(l<r){
        ll mid=(l+r)>>1;
        mergesort(l,mid);
        mergesort(mid+1,r);
        merge_(l,mid,r);
    }
}
signed main(){
    ios::sync_with_stdio(false);
    cin.tie(0);cout.tie(0);
    int n;
    while(cin>>n && n!=0){
        memset(a,0,sizeof(a));
        ans=0;
        for(int i=0;i<n;i++) cin>>a[i];
        mergesort(0,n-1);
        cout<<ans<<endl;
    }    
    return 0;
}

2388 -- Who's in the Middle (poj.org)

#include<iostream>//找中间数 
using namespace std;
const int N=10010;
int data[N];
#define swap(a,b){int tmp=a;a=b;b=tmp;}
int partition(int left,int right){
    int i=left;
    int tmp=data[right];
    for(int j=left;j<right;j++){
        if(data[j]<tmp){
            swap(data[j],data[i]);
            i++;
        }
    }
    swap(data[i],data[right]);
    return i;
}
void quicksort(int left,int right){
    if(left<right){
        int i=partition(left,right);
        partition(left,i-1);
        partition(i+1,right);
    }
}
signed main(){
    ios::sync_with_stdio(false);
    cin.tie(0);cout.tie(0);
    int n;
    cin>>n;
    for(int i=1;i<=n;i++) cin>>data[i];    
    quicksort(1,n);
    cout<<data[(n+1)/2]<<endl;;
    
    return 0;
}

hdu账号莫名用不了，用洛谷的题平替一下，仅用修改一步，即可通过

P1908 逆序对 - 洛谷 | 计算机科学教育新生态 (luogu.com.cn)

#include<iostream>//归并排序 
#include<cstring>
using namespace std;
typedef long long ll;
const int N=500010;
ll a[N],tmp[N],ans;
void merge_(ll l,ll mid,ll r){
    ll i=l,j=mid+1,t=0;
    while(i<=mid&&j<=r){
        if(a[i]>a[j]){
            tmp[t++]=a[j++];
            ans+=mid-i+1;
        }else tmp[t++]=a[i++];
    }
    while(i<=mid) tmp[t++]=a[i++];
    while(j<=r) tmp[t++]=a[j++];
    for(int i=0;i<t;i++) a[l+i]=tmp[i];
}
void mergesort(ll l,ll r){
    if(l<r){
        ll mid=(l+r)>>1;
        mergesort(l,mid);
        mergesort(mid+1,r);
        merge_(l,mid,r);
    }
}
signed main(){
    ios::sync_with_stdio(false);
    cin.tie(0);cout.tie(0);
    int n;
    cin>>n;
    memset(a,0,sizeof(a));
    ans=0;
    for(int i=0;i<n;i++) cin>>a[i];
    mergesort(0,n-1);
    cout<<ans<<endl;

    return 0;
}

hdu账号早日回归希望！

Problem - 1425 (hdu.edu.cn)

#include<iostream>//1425解法1 
#include<algorithm>
using namespace std;
const int N=1e6+10;
int n,m,a[N];
bool cmp(int a,int b){ return a>b;}
signed main(){
    //ios::sync_with_stdio(false);
    //cin.tie(0);cout.tie(0);
    while(scanf("%d%d",&n,&m)!=EOF){
        for(int i=1;i<=n;i++) scanf("%d",&a[i]);
        sort(a+1,a+1+n,cmp);
        for(int i=1;i<=m;i++) printf("%d ",a[i]);
    }
    
    return 0;
}

#include<iostream>//1425解法2 
#include<cstring>
using namespace std;
const int N=1e6+10;
int n,m,t,a[N];
signed main(){
    while(scanf("%d%d",&n,&m)!=EOF){
        for(int i=1;i<=n;i++){
            scanf("%d",&t);
            a[t+500000]=1;
        }
        for(int i=N;m>0;i--){
            if(a[i]){
                if(m>1) printf("%d ",i-500000);
                else printf("%d\n",i-500000);
                m--;
            }
        }
    }
    
    return 0;
}