主席树维护--可持久化数组

题意：https://www.luogu.org/problem/P3919

  1 #define IOS ios_base::sync_with_stdio(0); cin.tie(0);
  2 #include <cstdio>//sprintf islower isupper
  3 #include <cstdlib>//malloc  exit strcat itoa system("cls")
  4 #include <iostream>//pair
  5 #include <fstream>//freopen("C:\\Users\\13606\\Desktop\\草稿.txt","r",stdin);
  6 #include <bitset>
  7 //#include <map>
  8 //#include<unordered_map>
  9 #include <vector>
 10 #include <stack>
 11 #include <set>
 12 #include <string.h>//strstr substr
 13 #include <string>
 14 #include <time.h>//srand(((unsigned)time(NULL))); Seed n=rand()%10 - 0~9;
 15 #include <cmath>
 16 #include <deque>
 17 #include <queue>//priority_queue<int, vector<int>, greater<int> > q;//less
 18 #include <vector>//emplace_back
 19 //#include <math.h>
 20 //#include <windows.h>//reverse(a,a+len);// ~ ! ~ ! floor
 21 #include <algorithm>//sort + unique : sz=unique(b+1,b+n+1)-(b+1);+nth_element(first, nth, last, compare)
 22 using namespace std;//next_permutation(a+1,a+1+n);//prev_permutation
 23 //******************
 24 int abss(int a);
 25 int lowbit(int n);
 26 int Del_bit_1(int n);
 27 int maxx(int a,int b);
 28 int minn(int a,int b);
 29 double fabss(double a);
 30 void swapp(int &a,int &b);
 31 clock_t __STRAT,__END;
 32 double __TOTALTIME;
 33 void _MS(){__STRAT=clock();}
 34 void _ME(){__END=clock();__TOTALTIME=(double)(__END-__STRAT)/CLOCKS_PER_SEC;cout<<"Time: "<<__TOTALTIME<<" s"<<endl;}
 35 //***********************
 36 #define rint register int
 37 #define fo(a,b,c) for(rint a=b;a<=c;++a)
 38 #define fr(a,b,c) for(rint a=b;a>=c;--a)
 39 #define mem(a,b) memset(a,b,sizeof(a))
 40 #define pr printf
 41 #define sc scanf
 42 #define ls rt<<1
 43 #define rs rt<<1|1
 44 typedef long long ll;
 45 const double E=2.718281828;
 46 const double PI=acos(-1.0);
 47 //const ll INF=(1LL<<60);
 48 const int inf=(1<<30);
 49 const double ESP=1e-9;
 50 const int mod=(int)1e9+7;
 51 const int N=(int)1e6+10;
 52 int read(){
 53     int x=0,f=1;char ch=getchar();
 54     for(;!isdigit(ch);ch=getchar())if(ch==‘-‘)f=-1;
 55     for(;isdigit(ch);ch=getchar())x=x*10+ch-‘0‘;
 56     return x*f;
 57 }
 58 
 59 int tot;
 60 int root[N],lson[N*20],rson[N*20];
 61 int a[N],ans[N*20];
 62 
 63 void build(int &now,int l,int r)
 64 {
 65     now=++tot;
 66     if(l==r)
 67     {
 68         ans[now]=a[l];
 69         return;
 70     }
 71     int mid=(l+r)>>1;
 72     build(lson[now],l,mid);
 73     build(rson[now],mid+1,r);
 74 }
 75 void update(int &now,int pre,int l,int r,int pos,int val)
 76 {
 77     now=++tot;
 78     lson[now]=lson[pre];
 79     rson[now]=rson[pre];
 80     if(l==r)
 81     {
 82         ans[now]=val;
 83         return;
 84     }
 85     int mid=(l+r)>>1;
 86     if(pos<=mid)update(lson[now],lson[pre],l,mid,pos,val);
 87     else update(rson[now],rson[pre],mid+1,r,pos,val);
 88 }
 89 int Query(int l,int r,int pos,int rt)
 90 {
 91     if(l==r)
 92         return ans[rt];
 93     int mid=(l+r)>>1;
 94     if(pos<=mid)return Query(l,mid,pos,lson[rt]);
 95     else return Query(mid+1,r,pos,rson[rt]);
 96 }
 97 
 98 int main()
 99 {
100     int n=read(),m=read();
101     for(int i=1;i<=n;++i)a[i]=read();
102     tot=-1;
103     build(root[0],1,n);
104     int version,op,pos,val;
105     for(int i=1;i<=m;++i)
106     {
107         version=read();op=read();pos=read();
108         if(op==1)
109             val=read(),update(root[i],root[version],1,n,pos,val);
110         else
111             pr("%d\n",Query(1,n,pos,root[version])),root[i]=root[version];
112     }
113     return 0;
114 }
115 
116 /**************************************************************************************/
117 
118 int maxx(int a,int b)
119 {
120     return a>b?a:b;
121 }
122 
123 void swapp(int &a,int &b)
124 {
125     a^=b^=a^=b;
126 }
127 
128 int lowbit(int n)
129 {
130     return n&(-n);
131 }
132 
133 int Del_bit_1(int n)
134 {
135     return n&(n-1);
136 }
137 
138 int abss(int a)
139 {
140     return a>0?a:-a;
141 }
142 
143 double fabss(double a)
144 {
145     return a>0?a:-a;
146 }
147 
148 int minn(int a,int b)
149 {
150     return a<b?a:b;
151 }