pascal triangle

day0730.dart

// pascal triangle

void main() {
  print(pascalTriangle(5)); // [[1], [1, 1], [1, 2, 1], [1, 3, 3, 1], [1, 4, 6, 4, 1]]
  print("--------------------------");
  print(pascalTriangle(1)); // should return 1
  print("--------------------------");
  print(pascalTriangle(0)); // should return empty []
  print("--------------------------");
  print(pascalTriangle(-6)); // should return -1
}

  List<List<int>> pascalTriangle(int n) { // where n is number of rows
    List<List<int>> triangle = []; // initialize so [] can be returned when rows == 0
    if (n<0){
      triangle=[[-1]]; // where we input negative number returns -1
    }
    for (var row = 0; row < n; row++) {
      List<int> currentRow = [1]; // initialize current row such that return [1] when row == 1
      if (row >= 2) { // when row is from 2 upwards
        for (var j = 0; j < triangle[row - 1].length - 1; j++) {
          currentRow.add(triangle[row - 1][j] + triangle[row - 1][j + 1]);
        }
      }
      if (row >= 1) {
        currentRow.add(1);
      }
      triangle.add(currentRow);
    }
    return triangle;
  }