LG题单笔记 4
-对应章节 2.2
2.2 排序算法
P1059 明明的随机数
https://www.luogu.com.cn/problem/P1059
#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
int n,x;
vector<int> q;
int main(){
cin>>n;
for(int i=0;i<n;i++) {
cin>>x;q.push_back(x);
}
sort(q.begin(),q.end());
q.erase(unique(q.begin(),q.end()),q.end());
cout<<q.size()<<endl;
for(int i=0;i<q.size();i++) cout<<q[i]<<" ";
return 0;
}
P1068 分数线划定
https://www.luogu.com.cn/problem/P1068
#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
typedef pair<int,int> PII;
int n,m,k,s;
vector<PII> q;
bool cmp(PII a,PII b){
if(a.first!=b.first) return a.first>b.first;
else return a.second<b.second;
}
int main(){
cin>>n>>m;
for(int i=0;i<n;i++){
scanf("%d%d",&k,&s);
q.push_back({s,k});
}
sort(q.begin(),q.end(),cmp);
int rank=m*1.5-1;
while(rank<n-1&&q[rank+1].first==q[rank].first) rank++;//忘写.first导致虚空debug好久OTZ
cout<<q[rank].first<<" "<<rank+1<<endl;
for(int i=0;i<=rank;i++)
cout<<q[i].second<<" "<<q[i].first<<endl;
return 0;
}
P1051 谁拿了最多奖学金
https://www.luogu.com.cn/problem/P1051
写的时候感觉难度不够普及-,以为是自己的方法太丑陋了,但看题解也是循环一堆if OTZ
#include<iostream>
#include<vector>
using namespace std;
struct stu{
string name;
int te,re,sci;
char cad,wes;
int bon=0;
};
int n,mx,sum;
int main(){
cin>>n;
vector<stu> q(n+5);
for(int i=0;i<n;i++){
cin>>q[i].name>>q[i].te>>q[i].re>>q[i].cad>>q[i].wes>>q[i].sci;
}
for(int i=0;i<n;i++){
if(q[i].sci&&q[i].te>80) q[i].bon+=8000;
if(q[i].te>85&&q[i].re>80) q[i].bon+=4000;
if(q[i].te>90) q[i].bon+=2000;
if(q[i].wes=='Y'&&q[i].te>85) q[i].bon+=1000;
if(q[i].cad=='Y'&&q[i].re>80) q[i].bon+=850;
}
for(int i=0;i<n;i++){
if(q[i].bon>q[mx].bon) mx=i;
sum+=q[i].bon;
}
cout<<q[mx].name<<endl<<q[mx].bon<<endl;
cout<<sum;
return 0;
}
P1309 瑞士轮
https://www.luogu.com.cn/problem/P1309
本题用sort会被卡50,原因是本题用sort每次都对得分排序会造成明显的浪费,用归并排序解决本题最好。因为每轮比赛结束后,得分组和不得分组都是有序的,只需要一步merge即可。
而且需要静态实现,push_back用多了会卡一个TLE
#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;
const int N=1e5+5;
struct PII{
int first;
int second;
int pos;
};
int n,r,s,x;
int lb,rb;
bool cmp(PII a,PII b){
if(a.first!=b.first) return a.first>b.first;
else return a.pos<b.pos;
}
void merge(vector<PII> &q,PII l[],PII r[]){
int i=0,j=0,k=0;
while(i<lb&&j<rb) {
if(l[i].first>r[j].first) q[k++]=l[i++];
else if(l[i].first==r[j].first&&l[i].pos<r[j].pos) q[k++]=l[i++];
else q[k++]=r[j++];
}
while(i<lb) q[k++]=l[i++];
while(j<rb) q[k++]=r[j++];
}
int main(){
cin>>n>>r>>s;
vector<PII> q(2*n);
for(int i=0;i<2*n;i++){
scanf("%d",&x);
q[i].first=x;
}
for(int i=0;i<2*n;i++){
scanf("%d",&x);
q[i].second=x;
q[i].pos=i+1;
}
sort(q.begin(),q.end(),cmp);//刚开始需要全部排序
while(r--){
PII l[N],r[N];
lb=0,rb=0;
for(int i=0;i<2*n-1;i+=2){
if(q[i].second>q[i+1].second) {
q[i].first++;
r[rb++]=q[i];
l[lb++]=q[i+1];
}
else {
q[i+1].first++;
r[rb++]=q[i+1];
l[lb++]=q[i];
}
}
merge(q,l,r);
}
cout<<q[s-1].pos;
return 0;
}
P1908 逆序对
https://www.luogu.com.cn/problem/P1908
套模板,大雪菜唯一真神
#include<iostream>
using namespace std;
typedef long long lm;
const int N=500005;
int n;
int a[N],tmp[N];
lm merge_sort(int q[],int l,int r){
if(l>=r) return 0;
int mid=(l+r)>>1;
lm res=merge_sort(q,l,mid)+merge_sort(q,mid+1,r);
int k=0,i=l,j=mid+1;
while(i<=mid&&j<=r)
if(q[i]<=q[j]) tmp[k++]=q[i++];
else{
res+=mid-i+1;
tmp[k++]=q[j++];
}
while(i<=mid) tmp[k++]=q[i++];
while(j<=r) tmp[k++]=q[j++];
for(i=l,j=0;i<=r;i++,j++) q[i]=tmp[j];
return res;
}
int main(){
scanf("%d",&n);
for(int i=0;i<n;i++) scanf("%d",&a[i]);
cout<<merge_sort(a,0,n-1)<<endl;
return 0;
}