可持久化线段树_指针版本.

// 洛谷: https://www.luogu.org/problemnew/show/P3919

#include <bits/stdc++.h>

using namespace std;

const int maxn = 1e6+500;

#define lson rt->left
#define rson rt->right

struct nobe {
    int val;
    nobe *left;
    nobe *right;
    nobe () {
        val = 0;
        left = right = NULL;
    }
};

int date[maxn];
nobe *head[maxn];

void build(int l, int r, nobe* rt) {
    if (l == r) {
        rt->val = date[l];
        return ;
    }
    rt->left = new nobe();
    rt->right = new nobe();
    int m = (l + r) / 2;
    build(l, m, lson);
    build(m+1, r, rson);
}

int query(int l, int r, int id, nobe *rt) {
    if (l==id && r==id) return rt->val;
    int mid = (l + r) / 2;
    if (id <= mid) return query(l, mid, id, lson);
    return query(mid+1, r, id, rson);
}

void update(int l, int r, int id, int val, nobe *rt, nobe *nrt) {
    nrt->val = rt->val; 
    nrt->left = lson; nrt->right = rson;
    if (l==id && r==id) {
        nrt->val = val;
        return ;
    }
    int mid = (l + r) / 2;
    if (id <= mid) {
        nrt->left = new nobe();
        update(l, mid, id, val, lson, nrt->left);
    } else {
        nrt->right = new nobe();
        update(mid+1, r, id, val, rson, nrt->right);
    }
}

int main()
{
//    freopen("E:\\output.txt", "w", stdout);
//    freopen("E:\\input.txt", "r", stdin);
    int n, m, i, j;
    scanf("%d%d", &n, &m);
    for (i=1; i<=n; ++i) scanf("%d", date+i);
    head[0] = new nobe();
    build(1, n, head[0]);
    int vs, op, id, val;
    for (i=1; i<=m; ++i) {
        scanf("%d%d%d", &vs, &op, &id);
        if (op == 1) {
            scanf("%d", &val);
            head[i] = new nobe();
            update(1, n, id, val, head[vs], head[i]);    
        } else if (op == 2) {
            head[i] = head[vs];
            printf("%d\n", query(1, n, id, head[vs]));
        }
    }
    
    return 0;
}