HDU 3487：Play with Chain（Splay）

http://acm.hdu.edu.cn/showproblem.php?pid=3487

题意：有两种操作：1、Flip l r ，把 l 到 r 这段区间 reverse。2、Cut a b c ，把 a 到 b 这段区间切掉，再把这段区间接到切掉后的第 c 个数的后面。

思路：做完了上一道变态题目，做这道题目如鱼得水。Cut的时候就是把a 到 b 放到keytree的位置，记录一下当前keytree的值，然后切掉，再把切掉后的第 c 个数转到 root 的位置，再把这个记录的值重新连接回去。要注意当全部询问结束了，要把所有的rev标记pushdown。

#include <cstdio>
#include <cstring>
#include <cmath>
#include <cstdlib>
#include <algorithm>
#include <string>
#include <iostream>
#include <stack>
#include <map>
#include <queue>
using namespace std;
#define N 300100
#define INF 0x3f3f3f3f
#define lson ch[x][0]
#define rson ch[x][1]
#define keytree ch[ch[root][1]][0]

struct SplayTree
{
    int num[N], rev[N], ch[N][2], fa[N], val[N], sz[N];
    int n, root, cnt, ans[N], tol;

    void PushDown(int x)
    {
        if(rev[x]) {
            swap(lson, rson);
            if(lson) rev[lson] ^= 1;
            if(rson) rev[rson] ^= 1;
            rev[x] = 0;
        }
    }

    void PushUp(int x)
    {
        sz[x] = sz[lson] + sz[rson] + 1;
    }

    int NewNode(int w, int f, int kind)
    {
        int x = ++cnt;
        ch[x][0] = ch[x][1] = rev[x] = 0;
        sz[x] = 1; val[x] = w; fa[x] = f;
        ch[f][kind] = cnt;
        return x;
    }

    void Build(int l, int r, int &x, int f, int kind)
    {
        if(l > r) return ;
        int m = (l + r) >> 1;
        x = NewNode(num[m], f, kind);
        Build(l, m - 1, ch[x][0], x, 0);
        Build(m + 1, r, ch[x][1], x, 1);
        PushUp(x);
    }

    void Init()
    {
        root = cnt = tol = 0;
        rev[0] = val[0] = fa[0] = sz[0] = ch[0][0] = ch[0][1] = 0;
        root = NewNode(0, 0, 0);
        ch[root][1] = NewNode(0, root, 1);
        sz[root] = 2;
        Build(1, n, keytree, ch[root][1], 0);
        PushUp(ch[root][1]); PushUp(root);
    }

    void Rotate(int x, int kind)
    {
        int y = fa[x], z = fa[y];
        PushDown(y); PushDown(x);
        ch[y][!kind] = ch[x][kind];
        if(ch[y][!kind]) fa[ch[y][!kind]] = y;
        if(z) {
            if(y == ch[z][0]) ch[z][0] = x;
            else ch[z][1] = x;
        }
        fa[x] = z; fa[y] = x;
        ch[x][kind] = y;
        PushUp(y);
    }

    void Splay(int x, int goal)
    {
        while(fa[x] != goal) {
            int y = fa[x], z = fa[y];
            PushDown(z); PushDown(y); PushDown(x);
            int kind1 = x == ch[y][0];
            int kind2 = y == ch[z][0];
            if(z == goal) {
                Rotate(x, kind1);
            } else {
                if(kind1 == kind2) {
                    Rotate(y, kind1);
                } else {
                    Rotate(x, kind1);
                }
                Rotate(x, kind2);
            }
        }
        PushUp(x);
        if(goal == 0) root = x;
    }

    void RTO(int k, int goal)
    {
        int x = root;
        PushDown(x);
        while(k != sz[lson] + 1) {
            if(k <= sz[lson]) x = lson;
            else k -= sz[lson] + 1, x = rson;
            PushDown(x);
        }
        Splay(x, goal);
    }

    void Cut(int l, int r, int c)
    {
        RTO(l, 0);
//        Debug();
        RTO(r + 2, root);
        int tmp = keytree;
        keytree = 0;
//        Debug();
        RTO(c + 1, 0);
//        Debug();
        RTO(c + 2, root);
        fa[tmp] = ch[root][1];
        keytree = tmp;
    }

    void Reverse(int l, int r)
    {
        RTO(l, 0); RTO(r + 2, root);
        rev[keytree] ^= 1;
    }

    void Down(int x)
    {
        PushDown(x);
        if(lson) Down(lson);
        if(rson) Down(rson);
    }

    void Travel(int x)
    {
        if(lson) Travel(lson);
        ans[tol++] = val[x];
        if(rson) Travel(rson);
    }

    void Debug()
    {
        Down(root);
        Travel(root);
        for(int i = 1; i <= n; i++) {
            if(i == n) printf("%d
", ans[i]);
            else printf("%d ", ans[i]);
        }
    }
}spy;

int main()
{
    int n, m;
    while(scanf("%d%d", &n, &m)) {
        if(n < 0 || m < 0) break;
        spy.n = n;
        for(int i = 1; i <= n; i++) spy.num[i] = i;
        spy.Init();
        while(m--) {
            char s[10];
            int a, b, c;
            scanf("%s", s);
            if(s[0] == 'C') {
                scanf("%d%d%d", &a, &b, &c);
                spy.Cut(a, b, c);
            } else {
                scanf("%d%d", &a, &b);
                spy.Reverse(a, b);
            }
        }
        spy.Debug();
    }
    return 0;
}