洛谷.3919.[模板]可持久化数组(可持久化线段树/平衡树)

题目链接

//利用先前的根节点建树 想一下不难写。
#include <cstdio>
#include <cctype>
//#define gc() getchar()
#define gc() (SS==TT&&(TT=(SS=IN)+fread(IN,1,MAXIN,stdin),SS==TT)?EOF:*SS++)
const int N=1e6+5,MAXIN=2e6;int n,q,root[N],A[N];
char IN[MAXIN],*SS=IN,*TT=IN;
struct Seg_Tree
{#define lson son[x][0]#define rson son[x][1]int tot,val[N*21],son[N*21][2];void Build(int &x,int l,int r){x=++tot;if(l==r) val[x]=A[l];else{int m=l+r>>1;Build(lson,l,m), Build(rson,m+1,r);}}void Modify(int x,int &y,int l,int r,int p,int v){y=++tot;if(l==r) val[y]=v;else{int m=l+r>>1;if(p<=m) son[y][1]=rson, Modify(lson,son[y][0],l,m,p,v);else son[y][0]=lson, Modify(rson,son[y][1],m+1,r,p,v);}}int Query(int x,int l,int r,int p){if(l==r) return val[x];if(p<=(l+r>>1)) return Query(lson,l,l+r>>1,p);return Query(rson,(l+r>>1)+1,r,p);}
}t;
inline int read()
{int now=0,f=1;register char c=gc();for(;!isdigit(c);c=gc()) if(c=='-') f=-1;for(;isdigit(c);now=now*10+c-'0',c=gc());return now*f;
}int main()
{n=read(),q=read();for(int i=1; i<=n; ++i) A[i]=read();t.Build(root[0],1,n);for(int opt,ver,p,i=1; i<=q; ++i){ver=read(), opt=read(), p=read();if(opt==1) t.Modify(root[ver],root[i],1,n,p,read());else root[i]=root[ver], printf("%d\n",t.Query(root[i],1,n,p));}return 0;
}