[模板] 可持久化数组
[题目链接]
https://www.luogu.org/problemnew/show/P3919
[算法]
可持久化线段树模板
详见这篇文章 : https://www.cnblogs.com/RabbitHu/p/segtree.html
[代码]
#include<bits/stdc++.h> using namespace std; const int MAXN = 2e6 + 10; int n , m , version , idx; int a[MAXN] , sum[MAXN << 4] , root[MAXN << 4] , lson[MAXN << 4] , rson[MAXN << 4]; template <typename T> inline void chkmax(T &x,T y) { x = max(x,y); } template <typename T> inline void chkmin(T &x,T y) { x = min(x,y); } template <typename T> inline void read(T &x) { T f = 1; x = 0; char c = getchar(); for (; !isdigit(c); c = getchar()) if (c == '-') f = -f; for (; isdigit(c); c = getchar()) x = (x << 3) + (x << 1) + c - '0'; x *= f; } inline void build(int &k , int l , int r) { k = ++idx; if (l == r) { sum[k] = a[l]; return; } int mid = (l + r) >> 1; build(lson[k] , l , mid); build(rson[k] , mid + 1 , r); sum[k] = sum[lson[k]] + sum[rson[k]]; } inline void modify(int &k , int old , int l , int r , int pos , int value) { k = ++idx; lson[k] = lson[old] , rson[k] = rson[old]; if (l == r) { sum[k] = value; return; } int mid = (l + r) >> 1; if (mid >= pos) modify(lson[k] , lson[k] , l , mid , pos , value); else modify(rson[k] , rson[k] , mid + 1 , r , pos , value); sum[k] = sum[lson[k]] + sum[rson[k]]; } inline int query(int &k , int old , int l , int r , int pos) { k = ++idx; lson[k] = lson[old] , rson[k] = rson[old]; sum[k] = sum[old]; if (l == r) return sum[k]; int mid = (l + r) >> 1; if (mid >= pos) return query(lson[k] , lson[k] , l , mid , pos); else return query(rson[k] , rson[k] , mid + 1 , r , pos); } int main() { read(n); read(m); for (int i = 1; i <= n; i++) read(a[i]); build(root[version = 0] , 1 , n); for (int i = 1; i <= m; i++) { int vi , type , loc; read(vi); read(type); read(loc); if (type == 2) { printf("%d\n" , query(root[i] , root[vi] , 1 , n , loc)); } else { int value; read(value); modify(root[i] , root[vi] , 1 , n , loc , value); } } return 0; }