class Clearer {
public:
    vector<vector<int> > clearZero(vector<vector<int> > mat, int n) {
        // write code here
        vector<pair<int,int> > vec;
        for(int i = 0;i < n;++i){
            for(int j = 0;j < n;++j){
                if(mat[i][j] == 0)
                   vec.push_back(pair<int,int>(i,j));
            }
        }
        for(int k = 0,i,j;k < vec.size();++k){
            i = vec[k].first;
            j = vec[k].second;
            //行
            for(int row = 0;row < n;++row)
                mat[row][j] = 0;
            //列
            for(int col = 0;col < n;++col)
                mat[i][col] = 0;
        }
        return mat;
    }
};