// Package pascal computes Pascal's triangle
package pascal
// Triangle returns a triangle based on input.
func Triangle(lines int) [][]int {
	ret := make([][]int, lines)
	for i := 0; i < lines; i++ {
		ret[i] = make([]int, i+1)
		for j := 0; j < len(ret[i]); j++ {
			var left, right int
			// handle out of range
			if i-1 >= 0 {
				if j-1 >= 0 {
					left = ret[i-1][j-1]
				}
				if j < len(ret[i])-1 { // previous line is shorter with 1
					right = ret[i-1][j]
				}
			}
			if left+right == 0 {
				ret[i][j] = 1
			} else {
				ret[i][j] = left + right
			}
		}
	}
	return ret
}