题解

#include <bits/stdc++.h>
using namespace std;
bool visit[101][101];
int test=0,n,m,a[101][101];
int dis[4][2] = {0,1,1,0,0,-1,-1,0};
void dfs(int x,int y)
{
    visit[x][y] = 1;
    test++;
    for (int i=0;i<4;i++)
    {
        int dx = x + dis[i][0];
        int dy = y + dis[i][1];
        if (dx < 0 || dx >= n || dy < 0 || dy >= m)continue;
        if (a[dx][dy] == 0 || visit[dx][dy])continue;
        dfs(dx,dy);
    }
}
int main()
{
    cin >> n >> m;
    for (int i=0;i<n;i++)
    {
        for (int j=0;j<m;j++)
        {
            cin >> a[i][j];
        }
    }
    int max1=0;
    for (int i=0;i<n;i++)
    {
        for (int j=0;j<m;j++)
        {
            if (a[i][j] == 1 && visit[i][j] == 0)
            {
                dfs(i,j);
                max1 = max(max1,test);
                test = 0;
            }
        }
    }
    cout << max1;
    return 0;
}