P3369 【模板】普通平衡树 splay解法

P3369 【模板】普通平衡树

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#include <bits/stdc++.h> using namespace std; const int N = 200005; int ch[N][2], par[N], val[N], cnt[N], size[N], ncnt, root; bool chk(int x) {     return ch[par[x]][1] == x; } void pushup(int x) {     size[x] = size[ch[x][0]] + size[ch[x][1]] + cnt[x]; } void rotate(int x) {     int y = par[x], z = par[y], k = chk(x), w = ch[x][k^1];     ch[y][k] = w; par[w] = y;     ch[z][chk(y)] = x; par[x] = z;     ch[x][k^1] = y; par[y] = x;     pushup(y); pushup(x); } void splay(int x, int goal = 0) {     while (par[x] != goal) {         int y = par[x], z = par[y];         if (z != goal) {             if (chk(x) == chk(y)) rotate(y);             else rotate(x);         }         rotate(x);     }     if (!goal) root = x; } void insert(int x) {     int cur = root, p = 0;     while (cur && val[cur] != x) {         p = cur;         cur = ch[cur][x > val[cur]];     }     if (cur) {         cnt[cur]++;     } else {         cur = ++ncnt;         if (p) ch[p][x > val[p]] = cur;         ch[cur][0] = ch[cur][1] = 0;         par[cur] = p; val[cur] = x;         cnt[cur] = size[cur] = 1;     }     splay(cur); } void find(int x) {     int cur = root;     while (ch[cur][x > val[cur]] && x != val[cur]) {         cur = ch[cur][x > val[cur]];     }     splay(cur); } int kth(int k) {     int cur = root;     while (1) {         if (ch[cur][0] && k <= size[ch[cur][0]]) {             cur = ch[cur][0];         } else if (k > size[ch[cur][0]] + cnt[cur]) {             k -= size[ch[cur][0]] + cnt[cur];             cur = ch[cur][1];         } else {             splay(cur);             return cur;         }     } } int pre(int x) {     find(x);     if (val[root] < x) return root;     int cur = ch[root][0];     while (ch[cur][1]) cur = ch[cur][1];     splay(cur);     return cur; } int succ(int x) {     find(x);     if (val[root] > x) return root;     int cur = ch[root][1];     while (ch[cur][0]) cur = ch[cur][0];     splay(cur);     return cur; } void remove(int x) {     int last = pre(x), next = succ(x);     splay(last); splay(next, last);     int del = ch[next][0];     if (cnt[del] > 1) {         cnt[del]--;         splay(del);     }     else ch[next][0] = 0;     pushup(next), pushup(root); } int n, op, x; int main() {     scanf("%d", &n);     insert(0x3f3f3f3f);     insert(0xcfcfcfcf);     while (n--) {         scanf("%d%d", &op, &x);         switch (op) {             case 1: insert(x); break;             case 2: remove(x); break;             case 3: find(x); printf("%d\n", size[ch[root][0]]); break;             case 4: printf("%d\n", val[kth(x+1)]); break;             case 5: printf("%d\n", val[pre(x)]); break;             case 6: printf("%d\n", val[succ(x)]); break;         }     } }