101. 孤岛的总面积
#include<bits/stdc++.h>
using namespace std;int dfs(vector<vector<int>>& mp, vector<vector<int>>& visit, int y, int x, int s, int& notEdge){if (mp[y][x] == 0 || visit[y][x] == 1) return s * notEdge;if (mp[y][x] == 1 && visit[y][x] == 0){s++;visit[y][x] = 1;}if (y == 0 || y == mp.size() - 1 || x == 0 || x == mp[0].size() - 1) notEdge = 0;if (y > 0) s = dfs(mp, visit, y - 1, x, s, notEdge);if (x > 0) s = dfs(mp, visit, y, x - 1, s, notEdge);if (y < mp.size() - 1) s = dfs(mp, visit, y + 1, x, s, notEdge);if (x < mp[0].size() - 1) s = dfs(mp, visit, y, x + 1, s, notEdge);return s * notEdge;
}int main(){int n, m;cin >> n >> m;int result = 0;vector<vector<int>> mp(n, vector<int>(m, 0));vector<vector<int>> visit(n, vector<int>(m, 0));for (int i = 0; i < n; i++){for (int j = 0; j < m; j++){cin >> mp[i][j];}}int isEdge;for (int i = 0; i < mp.size(); i++){for (int j = 0; j < mp[0].size(); j++){if (mp[i][j] == 1 && visit[i][j] == 0){isEdge = 1;result += dfs(mp, visit, i, j, 0, isEdge);}}}cout << result;return 0;
}dfs版本，在之前求总面积的基础上增加了判断是否有有边缘位置元素的部分，所以增加了一个notEdge变量，在遇到边缘元素时标记为0，以使所有输出均变为0，此外需要注意，即使遇到了边缘元素也需要先将所有陆地遍历并在visit上标记。毕竟做人需要有始有终）
#include<bits/stdc++.h>
using namespace std;int bfs(vector<vector<int>>& mp, vector<vector<int>>& visit, int y, int x){int result = 0;int notEdge = 1;queue<pair<int, int>> q;q.push({y, x});visit[y][x] = 1;result++;while(!q.empty()){pair<int, int> tmp = q.front();q.pop();int tmpy = tmp.first, tmpx = tmp.second;if (tmpy == 0 || tmpx == 0 || tmpy == mp.size() - 1 || tmpx == mp[0].size() - 1) notEdge = 0;if (tmpy > 0){if (mp[tmpy - 1][tmpx] == 1 && visit[tmpy - 1][tmpx] == 0){q.push({tmpy - 1, tmpx});visit[tmpy - 1][tmpx] = 1;result++;}}if (tmpx > 0){if (mp[tmpy][tmpx - 1] == 1 && visit[tmpy][tmpx - 1] == 0){q.push({tmpy, tmpx - 1});visit[tmpy][tmpx - 1] = 1;result++;}}if (tmpy < mp.size() - 1){if (mp[tmpy + 1][tmpx] == 1 && visit[tmpy + 1][tmpx] == 0){q.push({tmpy + 1, tmpx});visit[tmpy + 1][tmpx] = 1;result++;}}if (tmpx < mp[0].size() - 1){if (mp[tmpy][tmpx + 1] == 1 && visit[tmpy][tmpx + 1] == 0){q.push({tmpy, tmpx + 1});visit[tmpy][tmpx + 1] = 1;result++;}}}return result * notEdge;
}int main(){int n, m;cin >> n >> m;int result = 0;vector<vector<int>> mp(n, vector<int>(m, 0));vector<vector<int>> visit(n, vector<int>(m, 0));for (int i = 0; i < n; i++){for (int j = 0; j < m; j++){cin >> mp[i][j];}}for (int i = 0; i < mp.size(); i++){for (int j = 0; j < mp[0].size(); j++){if (mp[i][j] == 1 && visit[i][j] == 0){result += bfs(mp, visit, i, j);}}}cout << result;return 0;
}bfs的版本，bfs不需要做递归回溯，所以函数的变量还是不变，只需要在内部增加一个标记是否有边缘元素的变量即可。
101. 孤岛的总面积
