(搜索)

找到[row, col]对应的连通分量，搜索的时候判断该点是否属于边界点，是的话修改值

C++ 代码

class Solution {
public:
    vector<vector<int>> colorBorder(vector<vector<int>>& grid, int row, int col, int color) {
        int n = grid.size(), m = grid[0].size();
        vector<vector<int>> g = grid;
        int c = grid[row][col];
        typedef pair<int, int> PII;
        bool st[60][60];
        PII q[60 * 60];
        memset(st, 0, sizeof st);

        int hh = 0, tt = 0;
        q[0] = {row, col};
        st[row][col] = true;

        int dx[] = {-1, 0, 1, 0}, dy[] = {0, 1, 0, -1};

        while(hh <= tt)
        {
            auto t = q[hh++];
            for(int i = 0; i < 4; i++)
            {
                int x = t.first + dx[i], y = t.second + dy[i];
                // 找到连通分量的边界点
                if(!(x >= 0 && x < n && y >= 0 && y < m && grid[x][y] == c)) g[t.first][t.second] = color;
                else if(!st[x][y])
                {
                    st[x][y] = true;
                    q[++tt] = {x, y};
                }
            }
        }
        return g;
    }
};