AHU-61 Lake Counting (并查集）

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简单并查集

Code

#include<bits/stdc++.h>
using namespace std;
const int MAXN = 10000 + 10;
const int dx[] = {1, -1, 0, 0, 1, -1, 1, -1};
const int dy[] = {0, 0, 1, -1, 1, -1, -1, 1};
int node[MAXN], pre[MAXN];

int find(int x) {
    return pre[x] == x ? x : pre[x] = find(pre[x]);
}

void join(int x, int y) {
    int xx = find(x);
    int yy = find(y);
    if (xx != yy) {
        pre[yy] = xx;
    }
}

int main() {
    int n, m, z;
    while(~scanf("%d%d", &n, &m)) {
        getchar();
        char ch;
        for (int i = 0; i < n; ++i) {
            for (int j = 0; j <= m; ++j) { //j多循环一次读换行
                scanf("%c", &ch);
                z = i * m + j;
                if (ch == '.') node[z] = 0;
                else if (ch == 'W') node[z] = 1;
                pre[z] = z;
            }
        }
        for (int i = 0; i < n*m; ++i) {
            if (node[i] == 0) continue;
            int x = i / m, y = i % m;
            for (int j = 0; j < 8; ++j) {
                int nx = x + dx[j], ny = y + dy[j];
                if (nx < 0 || nx >= n || ny < 0 || ny >= m) continue;
                int nz = nx * m + ny;
                if (node[nz] == 1)
                    join(i, nz);
            }
        }
        set<int> root;
        for (int i = 0; i < n*m; ++i) {
            if (node[i] == 0) continue;
            int nroot = find(i);
            root.insert(nroot);
        }
        printf("%d
", root.size());
    }

    return 0;
}