Function trap2

trapping_rain_water_42/solution.go:38–87

trap2 worked, but ran out of memory on leetcode. This was my first pass at the problem. I didn't think clearly enough about the memory, which could've been a max(height) x len(height) matrix.

(height []int)

// I didn't think clearly enough about the memory, which
// could've been a max(height) x len(height) matrix.
func trap2(height []int) int {
	cols := len(height)
	rows := 0
	for _, h := range height {
		rows = int(math.Max(float64(h), float64(rows)))
	}

	repr := make([][]int, rows)
	for i := range repr {
		repr[i] = make([]int, cols)
	}

	fillCol := 0
	fillRow := rows - 1
	for _, h := range height {
		hDecr := h
		for hDecr > 0 {
			repr[fillRow][fillCol] = 1
			fillRow--
			hDecr--
		}
		fillCol++
		fillRow = rows - 1
	}

	waterCnt := 0
	for row := 0; row < rows; row++ {
		for col := 0; col < cols; col++ {
			if repr[row][col] == 1 {
				colCur := col + 1
				colCnt := 0
				foundWall := false
				for colCur < cols {
					if repr[row][colCur] == 1 {
						foundWall = true
						break
					}
					colCur++
					colCnt++
				}

				if foundWall {
					waterCnt += colCnt
				}
			}
		}
	}

	return waterCnt
}