649 finish

Author: aQua

Algorithms/0649.dota2-senate/dota2-senate.go

@@ -1,30 +1,36 @@
 package Problem0649
 
-var result = map[byte]string{
-	'R': "Radiant",
-	'D': "Dire",
-}
-
 func predictPartyVictory(senate string) string {
-	bs := make([]byte, 0, len(senate)*2)
-	bs = append(bs, []byte(senate)...)
-	return helper(bs)
-}
+	n := len(senate)
 
-func helper(bs []byte) string {
-	b := bs[0]
-	var i int
-	for i = 1; i < len(bs); i++ {
-		if bs[i] != b {
-			break
+	// qr 和 qd 按顺序保存了 r 和 d 的议员的索引号
+	qr := make([]int, 0, n)
+	qd := make([]int, 0, n)
+	for i, b := range senate {
+		if b == 'R' {
+			qr = append(qr, i)
+		} else {
+			qd = append(qd, i)
 		}
 	}
 
-	if i == len(bs) {
-		return result[b]
+	// 对议员来说，最优策略就是，把下一个对方党派的议员 ban 掉
+	for len(qr) > 0 && len(qd) > 0 {
+		ri := qr[0]
+		qr = qr[1:]
+		di := qd[0]
+		qd = qd[1:]
+		if ri < di {
+			// ri ban 掉了 di
+			// ri 的索引号 +n
+			qr = append(qr, ri+n)
+		} else {
+			qd = append(qd, di+n)
+		}
 	}
 
-	copy(bs[i:], bs[i+1:])
-	bs[len(bs)-1] = b
-	return helper(bs[1:])
+	if len(qr) > 0 {
+		return "Radiant"
+	}
+	return "Dire"
 }

Algorithms/0649.dota2-senate/dota2-senate_test.go

@@ -13,6 +13,11 @@ var tcs = []struct {
 	ans    string
 }{
 
+	{
+		"RRDDD",
+		"Radiant",
+	},
+
 	{
 		"DDRRR",
 		"Dire",