BZOJ 1500: [NOI2005]维修数列 Splay

题目：http://www.lydsy.com/JudgeOnline/problem.php?id=1500

解法：Crash大神的论文上有详细解题方法，实现加调试花了很久很久。然后总算A掉啦。这个题都没过，说

啥学过Splay啊。

///BZOJ 1500#include <bits/stdc++.h>using namespace std;const int inf = 1e9;const int maxn = 510010;#define key_val ch[ch[root][1]][0]int fa[maxn], ch[maxn][2], w[maxn], siz[maxn], sum[maxn], lmax[maxn], rmax[maxn], ans[maxn];bool rev[maxn];bool same[maxn];int a[maxn];char s[20];int st[maxn];int n, m, T, tot, root, top;int newnode(){    int num;    if(top) num=st[top--];    else num=++tot;    ch[num][0]=ch[num][1]=fa[num]=0;    same[num]=rev[num]=0;    siz[num]=1;    sum[num]=w[num]=rmax[num]=lmax[num]=-inf;    return num;}void pushup(int x){    if(!x) return;    siz[x]=siz[ch[x][0]]+siz[ch[x][1]]+1;    sum[x]=sum[ch[x][0]]+sum[ch[x][1]]+w[x];    lmax[x]=max(lmax[ch[x][0]], sum[ch[x][0]]+w[x]+max(0,lmax[ch[x][1]]));    rmax[x]=max(rmax[ch[x][1]], sum[ch[x][1]]+w[x]+max(0,rmax[ch[x][0]]));    ans[x]=max(max(ans[ch[x][0]],ans[ch[x][1]]), max(0,rmax[ch[x][0]])+w[x]+max(0,lmax[ch[x][1]]));}void reverse(int x){    if(!x) return;    swap(lmax[x], rmax[x]);    swap(ch[x][0], ch[x][1]);    rev[x]^=1;}void replace(int x, int d){    if(!x) return;    w[x]=d;    sum[x]=d*siz[x];    lmax[x]=rmax[x]=ans[x]=max(d,d*siz[x]);    same[x]=1;    rev[x]=0;}void pushdown(int x){    if(rev[x]){        if(ch[x][0]) reverse(ch[x][0]);        if(ch[x][1]) reverse(ch[x][1]);        rev[x]=0;    }    if(same[x]){        if(ch[x][0]) replace(ch[x][0], w[x]);        if(ch[x][1]) replace(ch[x][1], w[x]);        same[x]=0;    }}void rotate(int x){    int y = fa[x], kind = ch[y][1] == x;    pushdown(y), pushdown(x);    ch[y][kind] = ch[x][!kind];    fa[ch[y][kind]] = y;    ch[x][!kind] = y;    fa[x] = fa[y];    fa[y] = x;    ch[fa[x]][ch[fa[x]][1] == y] = x;    pushup(y), pushup(x);}void splay(int x, int goal){    while(fa[x] != goal)    {        int y = fa[x], z = fa[y];        if(z == goal) rotate(x);        else if((ch[y][1] == x) == (ch[z][1] == y)) rotate(y), rotate(x);        else rotate(x), rotate(x);    }    if(goal == 0) root = x;}int find_k(int x, int k){    pushdown(x);    if(siz[ch[x][0]]==k-1) return x;    if(siz[ch[x][0]]>k-1) return find_k(ch[x][0], k);    else return find_k(ch[x][1], k-siz[ch[x][0]]-1);}void build(int l, int r, int rt){    int mid = (l+r)/2;    w[rt]=a[mid];    if(l==r){        sum[rt]=lmax[rt]=rmax[rt]=ans[rt]=w[rt];        siz[rt]=1;        return;    }    if(l<mid){        ch[rt][0]=newnode();        fa[ch[rt][0]]=rt;        build(l,mid-1,ch[rt][0]);    }    if(mid<r){        ch[rt][1]=newnode();        fa[ch[rt][1]]=rt;        build(mid+1,r,ch[rt][1]);    }    pushup(rt);}int Query(int l, int num){    int x = find_k(root, l);    splay(x, 0);    int y = find_k(ch[x][1], num+1);    splay(y, x);    return sum[ch[y][0]];}void Insert(int l, int num){    for(int i=1; i<=num; i++) scanf("%d", &a[i]);    int x = find_k(root, l+1);    splay(x, 0);    int y = find_k(ch[x][1], 1);    splay(y, x);    ch[y][0] = newnode();    fa[ch[y][0]] = y;    build(1, num, ch[y][0]);    pushup(y);    pushup(x);}void Erase(int x){    if(!x) return ;    st[++top]=x;    if(ch[x][0]) Erase(ch[x][0]);    if(ch[x][1]) Erase(ch[x][1]);}void Delete(int l, int num){    int x = find_k(root, l);    splay(x, 0);    int y = find_k(ch[x][1], num+1);    splay(y, x);    Erase(ch[y][0]);    fa[ch[y][0]]=0;    ch[y][0]=0;    pushup(y);    pushup(x);}void Reverse(int l, int num){    int x = find_k(root, l);    splay(x, 0);    int y = find_k(ch[x][1], num+1);    splay(y, x);    reverse(ch[y][0]);    pushup(y);    pushup(x);}void Replace(int l, int num, int d){    int x = find_k(root, l);    splay(x, 0);    int y = find_k(ch[x][1], num+1);    splay(y, x);    replace(ch[y][0], d);    pushup(y);    pushup(x);}int main(){    lmax[0] = rmax[0] = ans[0] = -inf;    tot = 2;    root = 1;    fa[1] = 0;    siz[1] = 2;    ch[1][1] = 2;    w[1] = sum[1] = lmax[1] = rmax[1] = -inf;    fa[2] = 1;    siz[2] = 1;    w[2] = sum[2] = lmax[2] = rmax[2] = -inf;    int n, T;    scanf("%d%d", &n, &T);    for(int i=1; i<=n; i++) scanf("%d", &a[i]);    ch[2][0] = newnode(); fa[ch[2][0]] = 2;    build(1, n, ch[2][0]);    pushup(2);    pushup(1);    while(T--){        int x, y, z;        scanf("%s", s);        if(s[2] == 'X'){            printf("%d\n", ans[root]);        }        if(s[0] == 'G'){            scanf("%d%d", &x, &y);            printf("%d\n", Query(x, y));        }        if(s[0] == 'I'){            scanf("%d%d", &x,&y);            Insert(x, y);        }        if(s[0] == 'D'){            scanf("%d%d", &x,&y);            Delete(x, y);        }        if(s[0] == 'R'){            scanf("%d%d", &x,&y);            Reverse(x, y);        }        if(s[4] == '-'){            scanf("%d%d%d", &x,&y,&z);            Replace(x, y, z);        }    }    return 0;}