HDU-4453 Looploop（Splay树）

传送门：HDU-4453

题解：Splay树

如果要把指针从1移到2，可以把1先删除，再插入到n的后面，如果要把指针从1移动到n，可以把n删除，再插入到1的前面

#include<bits/stdc++.h>using namespace std;const int MX = 2e5 + 5;int m, k1, k2;int n;int a[MX];int root, rear;         //根节点,节点总数int rem[MX], tot;       //经过删除后未被使用的节点int ch[MX][2], fa[MX];int val[MX], col[MX], add[MX];int sz[MX];void NewNode(int &rt, int father, int v) {    if (tot) rt = rem[tot--];    else rt = ++rear;    fa[rt] = father;    ch[rt][0] = ch[rt][1] = col[rt] = add[rt] = 0;    val[rt] = v;    sz[rt] = 1;}void PushUP(int rt) {    int ls = ch[rt][0], rs = ch[rt][1];    sz[rt] = sz[ls] + sz[rs] + 1;}void PushDown(int rt) {    if (col[rt]) {        col[ch[rt][0]] ^= col[rt];        col[ch[rt][1]] ^= col[rt];        swap(ch[rt][0], ch[rt][1]);        col[rt] = 0;    }    if (add[rt]) {        add[ch[rt][0]] += add[rt];        add[ch[rt][1]] += add[rt];        val[ch[rt][0]] += add[rt];        val[ch[rt][1]] += add[rt];        add[rt] = 0;    }}void build(int &rt, int l, int r, int father) {    if (l > r) return;    int m = (l + r) >> 1;    NewNode(rt, father, a[m]);    build(ch[rt][0], l, m - 1, rt);    build(ch[rt][1], m + 1, r, rt);    PushUP(rt);}void init() {    root = rear = tot = 0;    NewNode(root, 0, 0);  //一共n+2个节点,0~n+1    NewNode(ch[root][1], root, 0);    for (int i = 1; i <= n; i++) scanf("%d", &a[i]);    build(ch[ch[root][1]][0], 1, n, ch[root][1]);    PushUP(root);}void Link(int x, int y, int c) {    fa[x] = y; ch[y][c] = x;}void Rotate(int x, int c) { //c=0表示左旋,c=1表示右旋    int y = fa[x];    PushDown(y);    PushDown(x);    Link(x, fa[y], ch[fa[y]][1] == y);    Link(ch[x][c], y, !c);    Link(y, x, c);    PushUP(y); //y变成x子节点,只要更新y}void Splay(int x, int f) {    PushDown(x);    while (fa[x] != f) {        int y = fa[x];        if (fa[y] == f) Rotate(x, ch[y][0] == x);        else {            int t = ch[fa[y]][0] == y;            if (ch[y][t] == x) Rotate(x, !t);            else Rotate(y, t);            Rotate(x, t);        }    }    PushUP(x);   //更新x    if (f == 0) root = x;}int get_kth(int rt, int k) {    PushDown(rt);    int t = sz[ch[rt][0]] + 1, ret;    if (t == k) ret = rt;    else if (t > k) ret = get_kth(ch[rt][0], k);    else ret = get_kth(ch[rt][1], k - t);    PushUP(rt);    return ret;}void Update(int L, int R, int v) {    Splay(get_kth(root, L), 0);    Splay(get_kth(root, R + 2), root);    int t = ch[ch[root][1]][0];    add[t] += v;    val[t] += v;}void Reverse(int L, int R) {    Splay(get_kth(root, L), 0);    Splay(get_kth(root, R + 2), root);    int t = ch[ch[root][1]][0];    col[t] ^= 1;}void Insert(int p, int v) {    Splay(get_kth(root, p + 1), 0); //将第p个数旋转到根节点    Splay(get_kth(root, p + 2), root); //将第p+1个数旋转到根节点的右儿子，此时该节点没有左儿子    NewNode(ch[ch[root][1]][0], ch[root][1], v);    PushUP(ch[root][1]);    PushUP(root);    n++;}void erase(int rt) {    if (!rt)return;    fa[rt] = 0;    rem[++tot] = rt;    n--;    erase(ch[rt][0]);    erase(ch[rt][1]);}int Delete(int p) {    Splay(get_kth(root, p), 0);       //将第p-1个数旋转到根节点    Splay(get_kth(root, p + 2), root);//将第p+1个数旋转到根节点的右儿子，此时该节点左儿子为p    int t = ch[ch[root][1]][0];    erase(t);    ch[ch[root][1]][0] = 0;    PushUP(ch[root][1]);    PushUP(root);    return t;}int Query(int p) {    Splay(get_kth(root, p + 1), 0);    //将第p个数旋转到根节点    return val[root];}void Move(int x) {    if (x == 1) {        int t = Delete(n);        Insert(0, val[t]);    } else {        int t = Delete(1);        Insert(n, val[t]);    }}int main() {    char op[10];    int x, cas = 0;    //freopen("in.txt","r",stdin);    while (scanf("%d%d%d%d", &n, &m, &k1, &k2), n || m || k1 || k2) {        printf("Case #%d:\n", ++cas);        init();        while (m--) {            scanf("%s", op);            if (op[0] == 'a') {                scanf("%d", &x);                Update(1, k2, x);            } else if (op[0] == 'r') Reverse(1, k1);            else if (op[0] == 'i') {                scanf("%d", &x);                Insert(1, x);            } else if (op[0] == 'd') {                Delete(1);            } else if (op[0] == 'm') {                scanf("%d", &x);                Move(x);            } else printf("%d\n", Query(1));        }    }    return 0;}