feat: progress

pkg/questions/word_ladder/main.go

@@ -0,0 +1,60 @@
+package wordladder
+
+import "iter"
+
+type wordSet map[string][]string
+
+func (w wordSet) add(word string) {
+	buffer := []byte(word)
+	for i := range word {
+		buffer[i] = '*'
+		w[string(buffer)] = append(w[string(buffer)], word)
+		buffer[i] = word[i]
+	}
+}
+
+func (w wordSet) neighborsOf(word string) iter.Seq[string] {
+	return func(yield func(string) bool) {
+		buffer := []byte(word)
+		for i := range word {
+			buffer[i] = '*'
+			for _, neighbor := range w[string(buffer)] {
+				yield(neighbor)
+			}
+			buffer[i] = word[i]
+		}
+	}
+}
+
+func ladderLength(beginWord string, endWord string, wordList []string) int {
+	ws := wordSet{}
+	for _, word := range wordList {
+		ws.add(word)
+	}
+
+	idx, iteration, visited := 0, []string{beginWord}, map[string]bool{}
+	visited[beginWord] = true
+
+	for {
+		nextIteration := []string{}
+		for _, it := range iteration {
+			if it == endWord {
+				return idx
+			}
+
+			for neighbor := range ws.neighborsOf(it) {
+				if visited[neighbor] {
+					continue
+				}
+
+				visited[neighbor] = true
+				nextIteration = append(nextIteration, neighbor)
+			}
+		}
+
+		iteration = nextIteration
+		idx++
+	}
+
+	return 0
+}