99 lines
2.1 KiB
C++
99 lines
2.1 KiB
C++
#include <algorithm>
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#include <cstdio>
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#include <cmath>
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#include <cstring>
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using namespace std;
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const int N = 1000010;
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struct Node {
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int l, r, v;
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} tr[N << 5];
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int root[N], idx;
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int n, m, a[N];
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//快读
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int read() {
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int x = 0, f = 1;
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char ch = getchar();
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while (ch < '0' || ch > '9') {
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if (ch == '-') f = -1;
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ch = getchar();
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}
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while (ch >= '0' && ch <= '9') {
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x = (x << 3) + (x << 1) + (ch ^ 48);
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ch = getchar();
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}
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return x * f;
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}
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// build的原因，是因为有初始值，版本0不是空的
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void build(int &u, int l, int r) {
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u = ++idx;
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if (l == r) {
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tr[u].v = a[l];
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return;
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}
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int mid = (l + r) >> 1;
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build(tr[u].l, l, mid);
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build(tr[u].r, mid + 1, r);
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}
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void update(int &u, int l, int r, int x, int v) {
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tr[++idx] = tr[u];
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u = idx;
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if (l == r) {
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tr[idx].v = v;
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return;
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}
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int mid = (l + r) >> 1;
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if (mid >= x)
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update(tr[u].l, l, mid, x, v);
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else
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update(tr[u].r, mid + 1, r, x, v);
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}
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int query(int u, int l, int r, int x) {
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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 (mid >= x)
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return query(tr[u].l, l, mid, x);
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else
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return query(tr[u].r, mid + 1, r, x);
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}
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/*
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答案：
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59
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87
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41
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87
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88
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46
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*/
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int main() {
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//文件输入输出
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#ifndef ONLINE_JUDGE
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freopen("P3919.in", "r", stdin);
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#endif
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n = read(), m = read();
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for (int i = 1; i <= n; i++) a[i] = read();
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//构建主席树,因为有初始化值a[i]
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build(root[0], 1, n);
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for (int i = 1; i <= m; i++) {
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int x = read(), op = read(), y = read();
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if (op == 1) {
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// op=1:修改 x这个版本,管辖范围[1,n],将a[y]的值，即y这个位置,修改为v
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int v = read();
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root[i] = root[x];
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update(root[i], 1, n, y, v);
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} else {
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// op=2：访问版本x中，y这个位置上的值
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root[i] = root[x];
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printf("%d\n", query(root[i], 1, n, y));
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}
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}
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return 0;
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}
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