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https://git.sb/baoshuo/OI-codes.git
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101 lines
1.5 KiB
C++
101 lines
1.5 KiB
C++
#include <iostream>
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using std::cin;
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using std::cout;
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const char endl = '\n';
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const int N = 1e6 + 5;
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int n, m, a[N], root[N], cnt;
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struct node {
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int l, r, v;
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} tr[N << 6];
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int build(int l, int r) {
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int p = ++cnt;
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if (l == r) {
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tr[p].v = a[l];
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return p;
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}
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int mid = l + r >> 1;
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tr[p].l = build(l, mid);
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tr[p].r = build(mid + 1, r);
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return p;
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}
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int modify(int u, int l, int r, int p, int v) {
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int q = ++cnt;
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tr[q] = tr[u];
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if (l == r) {
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a[p] = v;
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tr[q].v = v;
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return q;
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}
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int mid = l + r >> 1;
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if (p <= mid) {
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tr[q].l = modify(tr[u].l, l, mid, p, v);
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} else {
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tr[q].r = modify(tr[u].r, mid + 1, r, p, v);
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}
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return q;
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}
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int query(int u, int l, int r, int p) {
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if (l == r) return tr[u].v;
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int mid = l + r >> 1;
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if (p <= mid) {
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return query(tr[u].l, l, mid, p);
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}
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return query(tr[u].r, mid + 1, r, p);
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}
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int main() {
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std::ios::sync_with_stdio(false);
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cin.tie(nullptr);
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cin >> n >> m;
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for (int i = 1; i <= n; i++) {
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cin >> a[i];
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}
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root[0] = build(1, n);
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for (int i = 1, ver, op; i <= m; i++) {
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cin >> ver >> op;
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if (op == 1) {
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int p, v;
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cin >> p >> v;
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root[i] = modify(root[ver], 1, n, p, v);
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} else { // op == 2
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int p;
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cin >> p;
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cout << query(root[ver], 1, n, p) << endl;
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root[i] = root[ver];
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}
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}
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return 0;
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}
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