59 lines
1.7 KiB
C++
59 lines
1.7 KiB
C++
#include <bits/stdc++.h>
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using namespace std;
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const int N = 1000 * 1000 + 10, M = N << 1;
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int n, m;
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// 二维转一维的办法,坐标从(1,1)开始
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int get(int x, int y) {
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// m为列宽
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return (x - 1) * m + y;
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}
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struct Edge {
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int a, b, c;
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const bool operator<(const Edge &t) const {
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return c < t.c;
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}
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} edge[M];
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int el;
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// 并查集
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int p[N];
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int find(int x) {
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if (p[x] != x) p[x] = find(p[x]);
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return p[x];
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}
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// 先连1的边，再连2的边
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void create_edges() {
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for (int i = 1; i <= (n - 1) * m; i++) // 前n-1行的每个点，都可以向下引一条边权为1的边
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edge[el++] = {i, i + m, 1}; // i -> i+m,边权为1
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for (int i = 1; i <= n * m; i++) { // 向右引边，注意最后一列不能向右引边
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if (i % m == 0) continue; // 最后一列放过
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edge[el++] = {i, i + 1, 2}; // i->i+1,边权为2
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}
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// 因为加进去就是按边权由小到大录入的，所以不用再排序了
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}
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int main() {
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cin >> n >> m;
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// 建边
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create_edges();
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// 并查集初始化
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for (int i = 1; i <= n * m; i++) p[i] = i;
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int x1, y1, x2, y2;
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// 利用二维转一维办法，将(x,y)映射成节点编号
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// 某些点之间已经有连线了=> 标识这些点已在并查集中
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while (cin >> x1 >> y1 >> x2 >> y2) {
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int a = get(x1, y1), b = get(x2, y2);
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p[find(a)] = find(b);
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}
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int res = 0; // 用Kruskal算法即可
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for (int i = 0; i < el; i++) {
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int a = find(edge[i].a), b = find(edge[i].b), c = edge[i].c;
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if (a != b) p[a] = b, res += c;
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}
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cout << res << endl;
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return 0;
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} |