Submission #826150

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Source Code Expand

#include <bits/stdc++.h>
using namespace std;

// memory: O(Q loglogN logN)
// mutable_get: O(loglogN logN)
// immutable_get: O(loglogN)
template<class T>
class Array {
public:
	Array() {}

	Array(int n) {
		h = 0;
		for (int i = 1; i < n; i *= 16) h += 4;
	}

	T *mutable_get(int k) {
		auto p = mutable_get(k, root, 0, h);
		root = p.first;
		return &p.second->value;
	}

	T immutable_get(int k) {
		return immutable_get(k, root, 0, h)->value;
	}

private:
	struct node {
		node *ch[16] = {};
		T value;

		node() {}
		node(T value) : value(value) {}
	};

	int h;
	node *root = nullptr;

	node *immutable_get(int a, node *x, int l, int d) {
		if (d == 0) return x;
		int id = (a - l) >> (d - 4);
		return immutable_get(a, x->ch[id], l + (id << (d - 4)), d - 4);
	}

	pair<node *, node *> mutable_get(int a, node *x, int l, int d) {
		x = x != nullptr ? new node(*x) : new node();
		if (d == 0) return make_pair(x, x);
		int id = (a - l) >> (d - 4);
		auto p = mutable_get(a, x->ch[id], l + (id << (d - 4)), d - 4);
		x->ch[id] = p.first;
		return make_pair(x, p.second);
	}
};

// root: O(logN loglogN)
// merge: O(logN loglogN)
struct UnionFind {
	struct node {
		int parent;
		int size;
	};

	Array<node> uf;

	UnionFind() : uf(0) {}

	UnionFind(int n) : uf(n) {
		for (int i = 0; i < n; i++) {
			node *nd = uf.mutable_get(i);
			nd->parent = i;
			nd->size = 1;
		}
	}

	int root(int x) {
		node nd = uf.immutable_get(x);
		if (nd.parent == x) return x;
		return root(nd.parent);
	}

	UnionFind merge(int x, int y) {
		x = root(x);
		y = root(y);
		if (x == y) return *this;

		node *u = uf.mutable_get(x);
		node *v = uf.mutable_get(y);

		u->parent = v->parent = u->size > v->size ? x : y;
		u->size = v->size = u->size + v->size;
		return *this;
	}

	int query(int x, int y) {
		x = root(x);
		y = root(y);
		if (x != y) {
			return uf.immutable_get(x).size + uf.immutable_get(y).size;
		} else {
			return uf.immutable_get(x).size;
		}
	}
};

int main() {
	int n, m;
	cin >> n >> m;

	vector<UnionFind> his(m + 1);
	UnionFind uf(n);

	for (int i = 0; i < m; i++) {
		int a, b;
		scanf("%d %d", &a, &b);
		a--;
		b--;
		uf.merge(a, b);
		his[i + 1] = uf;
	}

	int q;
	cin >> q;
	for (int i = 0; i < q; i++) {
		int x, y, z;
		scanf("%d %d %d", &x, &y, &z);
		x--;
		y--;

		int pass = m, fail = 0;
		while (pass - fail > 1) {
			int mid = (pass + fail) / 2;
			if (his[mid].query(x, y) >= z) {
				pass = mid;
			} else {
				fail = mid;
			}
		}
		printf("%d\n", pass);
	}
}

Submission Info

Compile Error

./Main.cpp: In function ‘int main()’:
./Main.cpp:114:25: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d %d", &a, &b);
                         ^
./Main.cpp:125:32: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d %d %d", &x, &y, &z);
                                ^

Judge Result