11922 - Permutation Transformer (Splay区间翻转)

UVA 11922 - Permutation Transformer

题目链接

题意：给一个序列，每次操作选择(a,b)，把(a,b)序列翻转之后加到末尾，求最终序列

思路：Splay的应用，多一个flip标记，在开头多一个虚拟的0结点，这样每次就利用Splay进行分裂合并即可

代码：

#include <cstdio>#include <cstring>#include <cstdlib>#include <algorithm>#include <vector>using namespace std;struct SplayTree {struct Node {Node *ch[2];int v, s;int flip;Node() {ch[0] = ch[1] = NULL;v = s = flip = 0;}Node(int v) {ch[0] = ch[1] = NULL; this->v = v; s = 1; flip = 0;}int cmp(int x) const {int d = x - ch[0]->s;if (d == 1) return -1;return d <= 0 ? 0 : 1;}void maintain() {s = ch[0]->s + ch[1]->s + 1;}void pushdown() {if (flip) {flip = 0;swap(ch[0], ch[1]);ch[0]->flip = !ch[0]->flip;ch[1]->flip = !ch[1]->flip;}}};Node *null;//0 is left, 1 is rightvoid rotate(Node* &o, int d) {Node *k = o->ch[d^1]; o->ch[d^1] = k->ch[d]; k->ch[d] = o;o->maintain(); k->maintain(); o = k;}void splay(Node * &o, int k) {o->pushdown();int d = o->cmp(k);if (d == 1) k -= o->ch[0]->s + 1;if (d != -1) {Node *p = o->ch[d];p->pushdown();int d2 = p->cmp(k);int k2 = (d2 == 0 ? k : k - p->ch[0]->s - 1);if (d2 != -1) {splay(p->ch[d2], k2);if (d == d2) rotate(o, d^1);else rotate(o->ch[d], d);}rotate(o, d^1);}}Node *merge(Node *left, Node *right) {splay(left, left->s);left->ch[1] = right;left->maintain();return left;}void split(Node *o, int k, Node* &left, Node* &right) {splay(o, k);left = o;right = o->ch[1];o->ch[1] = null;left->maintain();}int findkth(Node *o, int k, int flag) { //1 is bigth, 0 is smallthif (o == null || k <= 0 || k > o->s) return 0;int s = (o->ch[flag] == null ? 0 : o->ch[flag]->s);if (k == s + 1) return o->v;else if (k <= s) return findkth(o->ch[flag], k, flag);else return findkth(o->ch[flag^1], k - s - 1, flag);}void removetree(Node* &x) {if (x == NULL) return;if (x->ch[0] != NULL) removetree(x->ch[0]);if (x->ch[1] != NULL) removetree(x->ch[1]);delete x; x = NULL;}void init() {removetree(root);null = new Node();}void build(Node* &o, int l, int r) {if (l > r) {o = null;return;}int mid = (l + r) / 2;o = new Node(mid);build(o->ch[0], l, mid - 1);build(o->ch[1], mid + 1, r);o->maintain();}int n, m;Node *root;void print(Node* &o) {if (o != null) {o->pushdown();print(o->ch[0]);if (o->v >= 1)printf("%d\n", o->v);print(o->ch[1]);}}void solve() {init();build(root, 0, n);int a, b;while (m--) {scanf("%d%d", &a, &b);Node *left, *mid, *right, *o;split(root, a, left, o);split(o, b - a + 1, mid, right);mid->flip ^= 1;root = merge(merge(left, right), mid);}print(root);}} gao;int main() {while (~scanf("%d%d", &gao.n, &gao.m)) {gao.solve();}return 0;}