訓練日誌（二四年九月）

複習已學演算法，重視思維題

記得學字串和計算幾何

9.18

複習了離線二維數點：P2163和P10814
板子如下：

點選檢視程式碼

const int N = 2e6 + 5;
int n, m, a[N], ans[N];

struct Query {
	int p, q, x;
	Query(int p = 0, int q = 0, int x = 0) : p(p), q(q), x(x) {}
};

int c[N];
inline void update(int pos, int val) {
	for (; pos < N; pos += lowbit(pos)) c[pos] += val;
}

inline int query(int pos) {
	int ret = 0;
	for (; pos; pos -= lowbit(pos)) ret += c[pos];
	return ret;
}

vector <Query> v[N];

signed main(void) {
	read(n), read(m);
	for (int i = 1; i <= n; i++) read(a[i]);
	for (int i = 1; i <= m; i++) {
		int l, r, x;
		read(l), read(r), read(x);
		v[l - 1].push_back(Query(i, -1, x));
		v[r].push_back(Query(i, 1, x));
	}
	
	for (int i = 1; i <= n; i++) {
		update(a[i], 1);
		for (auto u : v[i]) ans[u.p] += u.q * query(u.x);
	}
	
	for (int i = 1; i <= m; i++) writeln(ans[i]);
	//fwrite(pf, 1, o1 - pf, stdout);
	return 0;
}