gistfile1.txt

import java.util.*;
import java.util.stream.IntStream;

import static java.util.stream.Collectors.toSet;

final class Matrix {

  private final List<List<Integer>> matrix;

  public Matrix(List<List<Integer>> matrix) {
    this.matrix = matrix;
  }

  public Collection<MatrixCoordinate> getSaddlePoints() {
    return IntStream.range(0, matrix.size())
            .mapToObj(
                    i -> IntStream.range(0, matrix.get(i).size())
                            .filter(j -> matrix.get(i).get(j) <= columnMin(j))
                            .filter(j -> matrix.get(i).get(j) >= rowMax(i))
                            .mapToObj(j -> new MatrixCoordinate(i, j))
                            .collect(toSet()))
            .flatMap(Set::stream).collect(toSet());
  }

  private int columnMin(final int number) {
    return matrix.stream().map(row -> row.get(number)).min(Integer::compareTo).orElseThrow(RuntimeException::new);
  }

  private int rowMax(final int number) {
    return matrix.get(number).stream().max(Integer::compareTo).orElseThrow(RuntimeException::new);
  }

}