[Union-Find] 백준 17619 개구리 점프 C++

 

https://www.acmicpc.net/problem/17619

17619번: 개구리 점프

#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

struct Position {
    int x1, x2, idx, y;
};

int parent[100001], cnt[100001];
vector<Position> v;

int find(int x) {
    if (x == parent[x]) return x;
    return parent[x] = find(parent[x]);
}

void unions(int x, int y) {
    x = find(x); y = find(y);
    if (x == y) return;
    if (cnt[x] < cnt[y]) swap(x, y);
    parent[y] = x; // x 개수 > y 개수 (y 트리 부모 = x 트리 루트)
    cnt[x] += cnt[y];
}

bool cmp(Position p1, Position p2) {
    return p1.x1 < p2.x1;
}

int main() {
	ios_base::sync_with_stdio(0);
	cin.tie(0); cout.tie(0); // 0 필수

    int n, q;
    cin >> n >> q;

    v.resize(n+1, {0, 0, 0, 0});
    int x1, x2, y;
    for(int i=1; i<=n; i++) { // 인덱스 맞추기
        cin >> x1 >> x2 >> y;
        v[i] = {x1, x2, i, y}; // 인덱스 저장 필수
        parent[i] = i;
        cnt[i] = 1;
    }

    sort(v.begin(), v.end(), cmp); // x1 오름차순 정렬

    for(int i=1; i<=n; i++) {
        for(int j=i+1; j<=n; j++) { // 건너건너 연결 가능
            if (v[i].x2 >= v[j].x1) unions(v[i].idx, v[j].idx);
            else break;
        }
    }

    for(int i=0; i<q; i++) {
        cin >> x1 >> x2;
        if (find(x1) == find(x2)) cout << "1\n";
        else cout << "0\n";
    }

	return 0;
}

#include<iostream>
#include<vector>
#include<algorithm>
using namespace std;

typedef struct pos {
    int x1, x2, idx;
};

int n, q, ans, x1, x2, y;
int par[100001], sze[100001];
vector<pos> v;

bool cmp(pos a, pos b) {
    return a.x1 < b.x1;
}

int find(int x) {
    if (x == par[x]) return x;
    return par[x] = find(par[x]);
}

void merge(int x, int y) {
    x = find(x); y = find(y);
    if (x == y) return;
    if (sze[x] < sze[y]) swap(x, y);
    par[y] = x;
    sze[x] += sze[y];
}

int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0), cout.tie(0);

    cin >> n >> q;

    v.push_back({ 0,0,0 });
    for (int i = 1; i <= n; i++) {
        cin >> x1 >> x2 >> y;
        v.push_back({ x1,x2,i });
        par[i] = i;
        sze[i] = 1;
    }

    sort(v.begin(), v.end(), cmp);

    for (int i = 1, j = 2; i <= n && j <= n;) {
        if (v[j].x1 <= v[i].x2) {
            merge(v[i].idx, v[j].idx);
            j++;
        }
        else i++;
    }

    for (int i = 0; i < q; i++) {
        cin >> x1 >> x2;
        if (find(x1) == find(x2)) cout << "1\n";
        else cout << "0\n";
    }
}