【第几小 / 分块】

题目

代码

#include <bits/stdc++.h>
using namespace std;const int N = 1e5+10;int a[N];
int br[N], bl[N], id[N], bcnt, L;
vector<int> bs[1010];int main()
{int n;cin >> n;for(int i = 1; i <= n; i++)cin >> a[i];L = sqrt(n + 1);for(int i = 1; i <= n; i += L) //只保证了左边界不越界{bcnt++;bl[bcnt] = i;br[bcnt] = min(i + L - 1, n); //这是分块最容易错误的点，就是没有考虑右边界越界for(int j = bl[bcnt]; j <= br[bcnt]; j++)bs[bcnt].push_back(a[j]), id[j] = bcnt; //想直接用下标访问未初始化的向量，需要resize}for(int i = 1; i <= bcnt; i++)sort(bs[i].begin(), bs[i].end());int m;cin >> m;for(int i = 1; i <= m; i++){int op;cin >> op;if(op == 1){int x, y;cin >> x >> y;int t = a[x];a[x] = y;int bid = id[x];auto it = lower_bound(bs[bid].begin(), bs[bid].end(), t);*it = y;sort(bs[bid].begin(), bs[bid].end());}else if(op == 2){int l, r, p;cin >> l >> r >> p;int cnt = 0;if(id[l] == id[r]){for(int j = l; j <= r; j++)if(a[j] < a[p]) cnt++;}else{for(int j = id[l] + 1; j < id[r]; j++){auto it = lower_bound(bs[j].begin(), bs[j].end(), a[p]);if(it == bs[j].end()) cnt += br[j] - bl[j] + 1;else cnt += (it - bs[j].begin());}for(int j = l; j <= br[id[l]]; j++)if(a[j] < a[p]) cnt++;for(int j = bl[id[r]]; j <= r; j++)if(a[j] < a[p]) cnt++;}cout << cnt + 1 << ' ';}}
}