hdu 4286 （list的reverse时间复杂度为n）

list 的翻转reverse源码：

// 将链表倒置
// 其算法核心是历遍链表, 每次取出一个结点, 并插入到链表起始点
// 历遍完成后链表满足倒置
template <class T, class Alloc>
void list<T, Alloc>::reverse()
{
  if (node->next == node || link_type(node->next)->next == node) return;
  iterator first = begin();
  ++first;
  while (first != end()) {
    iterator old = first;
    ++first;
    transfer(begin(), old, first);
  }
}  

直接用STL中的list华丽的超时代码：

#include<stdio.h>
#include<iostream>
#include<dequ>
#include<algorithm>
using namespace std;
list<int>li;
list<int>::iterator it,l,r;
int main()
{
    int _case,n;
    int i,x,lj,rj,step;
    scanf("%d",&_case);
    while(_case--)
    {
        li.clear();
        scanf("%d",&n);
        for(i=; i<n; i++)
        {
            scanf("%d",&x);
            li.push_back(x);
        }
        scanf("%d%d",&lj,&rj);
        l=li.begin();
        r=li.begin();
        for(i=;i<lj;i++)l++;
        for(i=;i<rj;i++)r++;
        scanf("%d",&step);
        for(i=; i<step; i++)
        {
            char s[];
            char c;
            getchar();
            scanf("%s",s);
            if(s[]=='I')
            {
                getchar();
                scanf("%c%d",&c,&x);
                //puts(c);
                //printf("%c",c);
                if(c=='L')// add before,f b
                {
                    l=li.insert(l,x);
                }
                else
                {
                    r++;
                    r=li.insert(r,x);
                }
            }
            else if(s[]=='D')
            {
                getchar();
                scanf("%c",&c);
                if(c=='R')
                {
                    r=li.erase(r);
                    if(r==li.end()&&r!=li.begin())r--;
                }
                else
                {
                    l=li.erase(l);
                    //if(l==li.end()&&l!=li.begin())l--;
                }
            }
            else if(s[]=='R')
            {
                if(r!=li.end())r++;
                reverse(l,r);
                r--;
            }
            else
            {
                getchar();
                scanf("%c",&c);
                if(s[]=='L')
                {

                    if(c=='L')
                    {
                        if(l!=li.begin())l--;
                    }
                    else
                    {
                        if(r!=li.begin())r--;
                        //printf("%%\n");
                    }
                }
                else
                {
                    if(c=='L')
                    {
                        if(l!=li.end())l++;
                    }
                    else
                    {
                        if(r!=li.end())r++;
                    }
                }
            }
            //cout<<*l<<' '<<*r<<endl;

        }
        it=li.begin();
        printf("%d",*it);
        it++;
        for(; it!=li.end(); it++)
            printf(" %d",*it);
        printf("\n");
    }

    return ;
}

 

数组模拟双向链表：

自己写的戳：

#include<stdio.h>
#define Max 1001000
struct node
{
    int fr;//front
    int be;//behind
    int val;//value
    bool flag;
} num[Max];;
//int
int n,m,l,r,x;
void Moveleft(char c)
{
    if(c=='L'&&num[l].fr!=)
        l=num[l].fr;
    else
        r=num[r].fr;
}

void Moveright(char c)
{
    if(c=='R'&&num[r].be!=n+)
        r=num[r].be;
    else
        l=num[l].be;
}
void InsertL()
{
    num[++n].val=x;
    num[n].flag=;
    num[n].fr=num[l].fr;
    num[n].be=l;
    num[num[l].fr].be=n;
    num[l].fr=n;

    l=n;//turn left;
}
void InsertR()
{
    printf("##");
    num[++n].val=x;
    num[n].flag=;
    num[n].fr=r;
    num[n].be=num[r].be;

    num[num[r].be].fr=n;
    num[r].be=n;
    r=n;
}
void DeleteL()
{
    num[num[l].fr].be=num[l].be;
    num[num[l].be].fr=num[l].fr;
    l=num[l].be;
}
void DeleteR()
{
    num[num[r].fr].be=num[l].be;
    num[num[r].be].fr=num[l].fr;
    r=num[r].fr;
}
void Reverse()
{

    num[r].flag=;
    //
    num[num[l].fr].be=r;
    num[num[r].be].fr=l;//num[l].fr;
    int x=num[l].fr;
    num[l].fr=num[r].be;
    num[r].be=x;

    num[num[l].fr].flag=l;

    //num[num[r].fr].flag=1;
    //num[r].be=num[r],fr;
}
void Myprintf()
{
    printf("##%d%d\n",l,r);
    int ret=;
    int x=;
    x=num[x].be;
    if(x!=m)printf("%d",num[x].val);
    ret^=num[x].flag;
        if(!ret)//equal 0
            x=num[x].be;
        else
            x=num[x].fr;

    while(x!=m)
    {

        printf(" %d",num[x].val);

        if(!ret)//equal 0
            x=num[x].be;
        else
            x=num[x].fr;
        ret^=num[x].flag;
        //printf("\n$%d$\n",ret);
    }
    printf("\n");
}
int main()
{
    int _case,step;
    int i;
    scanf("%d",&_case);
    while(_case--)
    {
        scanf("%d",&n);
        num[].be=;
        for(i=; i<=n; i++)
        {
            scanf("%d",&num[i].val);
            num[i].fr=i-;
            num[i].be=i+;
            num[i].flag=;
        }
        m=++n;
        scanf("%d %d",&l,&r);
        scanf("%d",&step);
        Myprintf();
        while(step--)
        {
            char op[],loc[];
            scanf("%s",op);
            if(op[]=='R')//reverse
                Reverse();
            else if(op[]=='I')//insert
            {
                scanf("%s %d",loc,&x);
                if(loc[]=='R')
                    InsertR();
                else
                    InsertL();
            }
            else if(op[]=='D')//delete
            {
                scanf("%s",loc);
                if(loc[]=='R')
                    DeleteR();
                else
                    DeleteL();
            }
            else//Move
            {
                scanf("%s",loc);
                if(op[]=='R')
                    Moveright(loc[]);
                else
                    Moveleft(loc[]);
            }
            Myprintf();
        }
        Myprintf();
    }
    return ;
}

参考代码（高明之处 运用了四个左右指针，判断相对位置）：

#include <iostream>
#include <cstdio>
#include <cstring>
using namespace std;

struct node
{
    int n1,n2,key;
};

node a[];
int L,R,e,n,C,Q,fL,fR;

void init()
{
    scanf("%d",&n);
    int i;
    for(i=; i<=n; i++)
    {
        scanf("%d",&a[i].key);
        a[i].n1=i-;
        a[i].n2=i+;
    }
    a[].n2=;
    a[n+].n1=n;
    e=n+;
    scanf("%d%d",&L,&R);
    fL=a[L].n1;
    fR=a[R].n2;
}

void moveLeftL()
{
    if(a[fL].n1==L) L=fL,fL=a[fL].n2;
    else L=fL,fL=a[fL].n1;
}

void moveLeftR()
{
    if(a[R].n1==fR) fR=R,R=a[R].n2;
    else fR=R,R=a[R].n1;
}

void moveRightL()
{
    if(a[L].n1==fL) fL=L,L=a[L].n2;
    else fL=L,L=a[L].n1;
}

void moveRightR()
{
    if(a[fR].n1==R) R=fR,fR=a[fR].n2;
    else R=fR,fR=a[fR].n1;
}

void insertL(int x)
{
    a[e].key=x;
    a[e].n1=fL;
    a[e].n2=L;
    if(a[fL].n1==L) a[fL].n1=e;
    else a[fL].n2=e;
    if(a[L].n1==fL) a[L].n1=e;
    else a[L].n2=e;
    L=e++;
}

void insertR(int x)
{
    a[e].key=x;
    a[e].n1=R;
    a[e].n2=fR;
    if(a[R].n1==fR) a[R].n1=e;
    else a[R].n2=e;
    if(a[fR].n1==R) a[fR].n1=e;
    else a[fR].n2=e;
    R=e++;
}

void deleteL()
{
    int next;
    if(a[L].n1==fL) next=a[L].n2;
    else next=a[L].n1;
    if(a[fL].n1==L) a[fL].n1=next;
    else a[fL].n2=next;
    if(a[next].n1==L) a[next].n1=fL;
    else a[next].n2=fL;
    L=next;
}

void deleteR()
{
    int next;
    if(a[R].n1==fR) next=a[R].n2;
    else next=a[R].n1;
    if(a[fR].n1==R) a[fR].n1=next;
    else a[fR].n2=next;
    if(a[next].n1==R) a[next].n1=fR;
    else a[next].n2=fR;
    R=next;
}

void reverse()
{
    if(a[fL].n1==L) a[fL].n1=R;
    else a[fL].n2=R;
    if(a[L].n1==fL) a[L].n1=fR;
    else a[L].n2=fR;
    if(a[R].n1==fR) a[R].n1=fL;
    else a[R].n2=fL;
    if(a[fR].n1==R) a[fR].n1=L;
    else a[fR].n2=L;

    int k;
    k=L;
    L=R;
    R=k;
}

void print()
{
    bool tag=false;
    fL=;
    L=a[fL].n2;
    while(L!=n+)
    {
        if(tag) putchar(' ');
        else tag=true;
        printf("%d",a[L].key);
        if(a[L].n1==fL) fL=L,L=a[L].n2;
        else fL=L,L=a[L].n1;
    }
    puts("");
}

int main()
{
    for(scanf("%d",&C); C--;)
    {
        init();
        scanf("%d",&Q);
        char op[],s[];
        int X;
        while(Q--)
        {
            scanf("%s",op);
            if(!strcmp(op,"MoveLeft"))
            {
                scanf("%s",s);
                if(s[]=='L') moveLeftL();
                else moveLeftR();
            }
            else if(!strcmp(op,"MoveRight"))
            {
                scanf("%s",s);
                if(s[]=='L') moveRightL();
                else moveRightR();
            }
            else if(!strcmp(op,"Insert"))
            {
                scanf("%s%d",s,&X);
                if(s[]=='L') insertL(X);
                else insertR(X);
            }
            else if(!strcmp(op,"Delete"))
            {
                scanf("%s",s);
                if(s[]=='L') deleteL();
                else deleteR();
            }
            else reverse();
        }
        print();
    }
    return ;
}