Hdu 4699 Editor(Splay)

题目大意：

给出一个文本编辑器，按照图示的操作进行删减和添加。

思路分析：

对于如何维护左边最大，就要记录每个区间的左边最大，还有这个节点的值，还有子区间的和。

注意看题目，题目的要求输出左边最大是不能为空集的，意味着如果全部都是负数，那么就输出最左边的负数就好。

那么就要解决初始化的问题。

再有一点问题就是会有很多个连续的L ，R操作。所以要判断边界。

#include <cstdio>#include <iostream>#include <vector>#include <cstdio>#include <stdlib.h>#define inf 0x3f3f3f3f#define maxn 2000005#define keyTree (ch[ch[root][1]][0])using namespace std;typedef long long LL;int S[maxn],que[maxn],ch[maxn][2],pre[maxn],siz[maxn];int root,top1,top2;/*以上变量为Splay固有的*/int val[maxn],a[maxn];int lef[maxn],sum[maxn];inline void scanf_(int &num){    char in;    bool neg=false;    while(((in=getchar()) > '9' || in<'0') && in!='-') ;    if(in=='-'){        neg=true;        while((in=getchar()) >'9' || in<'0');    }    num=in-'0';    while(in=getchar(),in>='0'&&in<='9')        num*=10,num+=in-'0';    if(neg)        num=0-num;}inline void printf_(int num){    bool flag=false;    if(num<0){        putchar('-');        num=-num;    }    int ans[10],top=0;    while(num!=0){        ans[top++]=num%10;        num/=10;    }    if(top==0)        putchar('0');    for(int i=top-1;i>=0;i--){        char ch=ans[i]+'0';        putchar(ch);    }}void Treaval(int x){    if(x)    {        Treaval(ch[x][0]);        printf("%d ",val[x]);        //printf("now %2d:lson  %2d rson %2d father %2d size = %2d ,val = %2d  \n",x,ch[x][0],ch[x][1],pre[x],siz[x],val[x]);        Treaval(ch[x][1]);    }}void debug(){    printf("root=%d\n",root);    Treaval(root);    puts("");}void New(int &x,int PRE,int v){    if(top2)x=S[--top2];    else x=++top1;    ch[x][0]=ch[x][1]=0;    siz[x]=1;    pre[x]=PRE;    val[x]=v;    lef[x]=v;   // rig[x]=max(0,v);    sum[x]=v;}void pushup(int x){    siz[x]=siz[ch[x][0]]+siz[ch[x][1]]+1;    sum[x]=sum[ch[x][0]]+sum[ch[x][1]]+val[x];    lef[x]=max(lef[ch[x][0]],max(sum[ch[x][0]]+val[x],sum[ch[x][0]]+val[x]+lef[ch[x][1]]));}void pushdown(int x){}void build(int &x,int s,int e,int f){    if(s>e)return;    int mid=(s+e)>>1;    New(x,f,a[mid]);    if(s<mid)build(ch[x][0],s,mid-1,x);    if(e>mid)build(ch[x][1],mid+1,e,x);    pushup(x);}void Rotate(int x,int kind){    int y=pre[x];    pushdown(x);    pushdown(y);    ch[y][!kind]=ch[x][kind];    pre[ch[x][kind]]=y;    if(pre[y])ch[pre[y]][ch[pre[y]][1]==y]=x;    pre[x]=pre[y];    ch[x][kind]=y;    pre[y]=x;    pushup(y);}void Splay(int x,int goal){    pushdown(x);    while(pre[x]!=goal)    {        if(pre[pre[x]]==goal)        Rotate(x,ch[pre[x]][0]==x);        else        {            int y=pre[x];            int kind=ch[pre[y]][0]==y;            if(ch[y][kind]==x){                Rotate(x,!kind);                Rotate(x,kind);            }            else {                Rotate(y,kind);                Rotate(x,kind);            }        }    }    pushup(x);    if(goal==0)root=x;}void RotateTo(int k,int goal){    int r=root;    pushdown(r);    while(siz[ch[r][0]]!=k)    {        if(k<siz[ch[r][0]])        {            r=ch[r][0];        }        else        {            k-=siz[ch[r][0]]+1;            r=ch[r][1];        }        pushdown(r);    }    Splay(r,goal);}void erase(int x){    int y=pre[x];    int head=0,tail=0;    for(que[tail++]=x;head<tail;head++)    {        S[top2++]=que[head];        if(ch[que[head]][0])que[tail++]=ch[que[head]][0];        if(ch[que[head]][1])que[tail++]=ch[que[head]][1];    }    ch[y][ch[y][1]==x]=0;    pushup(y);}void init(int n)/*special*/{    root=top1=top2=0;    ch[0][0]=ch[0][1]=siz[0]=pre[0]=sum[0]=0;    val[0]=0;    lef[0]=-0x3f3f3f3f;    New(root,0,0);    New(ch[root][1],root,0);    siz[root]=2;    pushup(ch[root][1]);    pushup(root);}int main(){    int Q;    while(scanf("%d",&Q)!=EOF)    {        init(1);        int pos=0;        int cnt=0;        while(Q--)        {            char cmd[5];            scanf("%s",cmd);            if(cmd[0]=='I')            {                int x;                scanf("%d",&x);                RotateTo(pos,0);                RotateTo(pos+1,root);                New(keyTree,ch[root][1],x);                pushup(ch[root][1]);                pushup(root);                cnt++;                pos++;            }            else if(cmd[0]=='Q')            {                int x;                scanf("%d",&x);                x=min(x,cnt);                RotateTo(0,0);                RotateTo(x+1,root);                printf_(lef[keyTree]);                puts("");            }            else if(cmd[0]=='D')            {                if(pos==0)continue;                RotateTo(pos-1,0);                RotateTo(pos+1,root);                keyTree=0;                pushup(ch[root][1]);                pushup(root);                if(pos)                pos--;                if(cnt>0)                cnt--;            }            else if(cmd[0]=='L')            {                pos--;                if(pos<0)pos=0;            }            else if(cmd[0]=='R')            {                pos++;                if(pos>cnt)pos=cnt;            }        }    }    return 0;}