LOJ - #6282. 数列分块入门 6

题目链接：https://ajax.loj.ac/problem/6282

#include<bits/stdc++.h>
#define ll long long
using namespace std;
const int maxn = 1e5 + 5;
int blo, opt, l, r, c, n, m;
int pos[maxn], a[maxn], st[maxn*2];
vector<int>ve[1005];
pair<int, int> query(int b)
{
    int x = 1;
    while(b > ve[x].size())
        b -= ve[x].size(),x++;
    return make_pair(x, b-1);
}
void rebuild()
{
    int top = 0;
    for (int i = 1; i <= m; i++){
        for (vector<int>:: iterator j = ve[i].begin(); j != ve[i].end(); j++)
            st[++top] = *j;
        ve[i].clear();
    }
    int blo2 = sqrt(top);
    for (int i = 1; i <= top; i++) ve[(i-1)/blo2+1].push_back(st[i]);
    m = (top - 1) /blo2 + 1;
}
void _insert(int a, int b)
{
    pair<int, int> t= query(a);
    ve[t.first].insert(ve[t.first].begin()+t.second, b);
    if(ve[t.first].size() > 20*blo)
        rebuild();
}
int main()
{
    scanf("%d", &n);
    blo = sqrt(n);
    for (int i = 1; i <= n; i++) scanf("%d", &a[i]), ve[(i-1)/blo+1].push_back(a[i]);
    m = (n-1) / blo + 1;
    for (int i = 0; i < n; i++){
        scanf("%d%d%d%d", &opt, &l, &r, &c);
        if(opt == 0) _insert(l, r);
        else {
            pair<int, int> t = query(r);
            printf("%d\n", ve[t.first][t.second]);
            }
    }

}