31

Author: TipsyPixie

README.md

@@ -47,5 +47,5 @@ Number | Difficulty | Asked By
 [#28](problem028) | MEDIUM | Palantir
 [#29](problem029) | EASY | Amazon
 [#30](problem030) | MEDIUM | Facebook
-[#31](problem031) | MEDIUM | Facebook
+[#31](problem031) | EASY | Google
 

problem028/problem028.go

@@ -16,7 +16,7 @@ func Justify(words []string, lineLength int) []string {
 			wordIndex++
 		} else {
 			justifiedWords = append(justifiedWords, justifyLine(lineSizeLeft, wordsInline, spaceCounts))
-			justifiedWords, lineSizeLeft, wordsInline, spaceCounts = initValues(words, lineLength)
+			_, lineSizeLeft, wordsInline, spaceCounts = initValues(words, lineLength)
 		}
 	}
 	justifiedWords = append(justifiedWords, justifyLine(lineSizeLeft, wordsInline, spaceCounts))
@@ -25,10 +25,10 @@ func Justify(words []string, lineLength int) []string {
 }
 
 func justifyLine(lineSizeLeft int, wordsInline []string, spaceCounts []int) string {
+	if len(wordsInline) == 1 {
+		spaceCounts = append(spaceCounts, 0)
+	}
 	for lineSize := 0; lineSize < lineSizeLeft; lineSize++ {
-		if len(wordsInline) == 1 {
-			spaceCounts = append(spaceCounts, 0)
-		}
 		spaceCounts[lineSize%len(spaceCounts)]++
 	}
 	if len(wordsInline) > 1 {

problem028/problem028_test.go

@@ -10,5 +10,6 @@ func TestJustify(t *testing.T) {
 	result := Justify(words, 16)
 	if !reflect.DeepEqual(result, []string{"the  quick brown", "fox  jumps  over", "the   lazy   dog"}) {
 		t.Fail()
+		t.Log(result)
 	}
 }

problem030/problem030.go

@@ -2,7 +2,7 @@ package problem030
 
 func MeasureTrappedWater(wallHeights []int) int {
 	trappedWater := 0
-	leftCursor, rightCursor := 0, len(wallHeights) - 1
+	leftCursor, rightCursor := 0, len(wallHeights)-1
 	leftMaxHeight, rightMaxHeight := 0, 0
 	for leftCursor <= rightCursor {
 		if leftHeight, rightHeight := wallHeights[leftCursor], wallHeights[rightCursor]; leftHeight < rightHeight {
@@ -22,6 +22,5 @@ func MeasureTrappedWater(wallHeights []int) int {
 		}
 	}
 
-
 	return trappedWater
 }

problem031/README.md

@@ -1,13 +1,9 @@
-## Daily Coding Problem: Problem #30 [Medium]
+## Daily Coding Problem: Problem #31 [EASY]
 
 Good morning! Here's your coding interview problem for today.
 
-This problem was asked by Facebook.
+This problem was asked by Google.
 
-You are given an array of non-negative integers that represents a two-dimensional elevation map where each element is unit-width wall and the integer is the height. Suppose it will rain and all spots between two walls get filled up.
+The edit distance between two strings refers to the minimum number of character insertions, deletions, and substitutions required to change one string to the other. For example, the edit distance between “kitten” and “sitting” is three: substitute the “k” for “s”, substitute the “e” for “i”, and append a “g”.
 
-Compute how many units of water remain trapped on the map in O(N) time and O(1) space.
-
-For example, given the input [2, 1, 2], we can hold 1 unit of water in the middle.
-
-Given the input [3, 0, 1, 3, 0, 5], we can hold 3 units in the first index, 2 in the second, and 3 in the fourth index (we cannot hold 5 since it would run off to the left), so we can trap 8 units of water.
+Given two strings, compute the edit distance between them.

problem031/problem031.go

@@ -1 +1,55 @@
 package problem031
+
+func minInt(nums ...int) int {
+	minimum := nums[0]
+	for _, num := range nums {
+		if num < minimum {
+			minimum = num
+		}
+	}
+	return minimum
+}
+
+func MeasureEditDistance(value1 string, value2 string) int {
+	// make sure width > height of the matrix
+	if len(value1) < len(value2) {
+		value1, value2 = value2, value1
+	}
+
+	matrixWidth, matrixHeight := len(value1)+1, len(value2)+1
+	distanceMatrix := make([][]int, matrixHeight, matrixHeight)
+	for rowIndex := range distanceMatrix {
+		distanceMatrix[rowIndex] = make([]int, matrixWidth, matrixWidth)
+	}
+
+	for initialRow, initialColumn := 0, 0; initialRow < matrixHeight && initialColumn < matrixWidth; {
+		for row, column := initialRow, initialColumn; 0 <= row && row < matrixHeight && 0 <= column && column < matrixWidth; {
+			switch {
+			case row == 0:
+				distanceMatrix[row][column] = column
+			case column == 0:
+				distanceMatrix[row][column] = row
+			default:
+				if value2[row-1] == value1[column-1] {
+					distanceMatrix[row][column] = distanceMatrix[row-1][column-1]
+				} else {
+					distanceMatrix[row][column] = 1 + minInt(
+						distanceMatrix[row-1][column],
+						distanceMatrix[row-1][column-1],
+						distanceMatrix[row][column-1],
+					)
+				}
+			}
+			row++
+			column--
+		}
+
+		if initialColumn < matrixWidth-1 {
+			initialColumn++
+		} else {
+			initialRow++
+		}
+	}
+
+	return distanceMatrix[matrixHeight-1][matrixWidth-1]
+}

problem031/problem031_test.go

@@ -1 +1,21 @@
 package problem031
+
+import (
+	"testing"
+)
+
+func TestMeasureEditDistance(t *testing.T) {
+	var editDistance int
+
+	editDistance = MeasureEditDistance("sitting", "kitten")
+	if editDistance != 3 {
+		t.Fail()
+		t.Log(editDistance)
+	}
+
+	editDistance = MeasureEditDistance("Saturday", "Sunday")
+	if editDistance != 3 {
+		t.Fail()
+		t.Log(editDistance)
+	}
+}