update

hard/488.zuma-game.go

@@ -0,0 +1,85 @@
+type pair struct { // The presentation of the board is the key!
+	_1 rune
+	_2 int
+}
+
+const INF int = 1e9
+
+func findMinStep(board string, hand string) int {
+	li := list.New()
+	n := len(board)
+	runes := []rune(board)
+	prev := pair{runes[0], 1}
+	for i := 1; i < n; i++ {
+		if runes[i] == prev._1 {
+			prev._2++
+		} else {
+			li.PushBack(prev)
+			prev = pair{runes[i], 1}
+		}
+	}
+	li.PushBack(prev)
+	m := make(map[rune]int)
+	for _, r := range hand {
+		m[r]++
+	}
+	// R, Y, B, G, W
+	if min := dfs(li, &m); min == INF {
+		return -1
+	} else {
+		return min
+	}
+}
+
+func dfs(li *list.List, m *map[rune]int) int {
+	clearBoard(li)
+	if li.Len() == 0 {
+		return 0
+	} else if len(*m) == 0 {
+		return INF
+	}
+	min := INF
+	for it := li.Front(); it != nil; it = it.Next() {
+		p := it.Value.(pair)
+		if cnt, ok := (*m)[p._1]; ok && 3 <= cnt+p._2 {
+			need := 3 - p._2
+			p._2 = 3
+			it.Value = p
+			(*m)[p._1] = cnt - need
+			if cnt == need {
+				delete(*m, p._1)
+			}
+			nli := list.New()
+			nli.PushBackList(li)
+			ret := dfs(nli, m) + need
+			if ret < min {
+				min = ret
+			}
+			p._2 -= need
+			it.Value = p
+			(*m)[p._1] = cnt
+		}
+	}
+	return min
+}
+
+func clearBoard(li *list.List) {
+	it := li.Front()
+	for it != nil {
+		if nxt := it.Next(); nxt != nil && nxt.Value.(pair)._1 == it.Value.(pair)._1 {
+			p := pair{it.Value.(pair)._1, it.Value.(pair)._2 + nxt.Value.(pair)._2}
+			it.Value = p
+			li.Remove(nxt)
+		} else if 3 <= it.Value.(pair)._2 {
+			pre := it.Prev()
+			li.Remove(it)
+			if pre != nil {
+				it = pre
+			} else {
+				it = nxt
+			}
+		} else {
+			it = nxt
+		}
+	}
+}