add new solutions

solutions/4/q433/solution.go

@@ -0,0 +1,71 @@
+package q433
+
+import "slices"
+
+func canMutate(a, b string) bool {
+	diff := false
+	for i := range len(a) {
+		if a[i] != b[i] {
+			if diff {
+				return false
+			}
+			diff = true
+		}
+	}
+	return diff // exactly one mutation
+}
+
+func minMutation(startGene string, endGene string, bank []string) int {
+	reachables := make([][]int, len(bank))
+	initial := []int{}
+	target := -1
+	for i := range len(bank) - 1 {
+		for j := i + 1; j < len(bank); j++ {
+			if canMutate(bank[i], bank[j]) {
+				reachables[i] = append(reachables[i], j)
+				reachables[j] = append(reachables[j], i)
+			}
+		}
+	}
+	for i := range bank {
+		if bank[i] == endGene {
+			target = i
+		}
+		if canMutate(startGene, bank[i]) {
+			if i == target {
+				return 1
+			}
+			initial = append(initial, i)
+		}
+	}
+	if target == -1 {
+		return -1
+	}
+
+	type qElem struct {
+		path []int
+	}
+	queue := make([]qElem, 0, len(initial)*2)
+	for _, i := range initial {
+		queue = append(queue, qElem{path: []int{i}})
+	}
+
+	for ; len(queue) > 0; queue = queue[1:] {
+		cur := queue[0].path
+		last := cur[len(cur)-1]
+		next := reachables[last]
+		for _, n := range next {
+			if n == target {
+				return len(cur) + 1
+			}
+			if slices.Contains(cur, n) {
+				continue
+			}
+			queue = append(queue, qElem{path: append(cur, n)})
+		}
+	}
+
+	return -1
+}
+
+var _ = minMutation