modify code

大厂刷题班/class14/Code03_BiggestBSTTopologyInTree.java

@@ -14,15 +14,26 @@ import java.io.StreamTokenizer;
 
 public class Code03_BiggestBSTTopologyInTree {
 
+	public static int MAXN = 200001;
+
+	public static int[][] tree = new int[MAXN][3];
+
+	public static int[] record = new int[MAXN];
+
 	public static void main(String[] args) throws IOException {
 		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
 		StreamTokenizer in = new StreamTokenizer(br);
 		PrintWriter out = new PrintWriter(new OutputStreamWriter(System.out));
 		while (in.nextToken() != StreamTokenizer.TT_EOF) {
 			int n = (int) in.nval;
+			for (int i = 1; i <= n; i++) {
+				tree[i][0] = 0;
+				tree[i][1] = 0;
+				tree[i][2] = 0;
+				record[i] = 0;
+			}
 			in.nextToken();
 			int h = (int) in.nval;
-			int[][] tree = new int[n + 1][3];
 			for (int i = 1; i <= n; i++) {
 				in.nextToken();
 				int c = (int) in.nval;
@@ -35,7 +46,7 @@ public class Code03_BiggestBSTTopologyInTree {
 				tree[c][1] = l;
 				tree[c][2] = r;
 			}
-			out.println(maxBSTTopology(h, tree, new int[n + 1]));
+			out.println(maxBSTTopology(h));
 			out.flush();
 		}
 	}
@@ -44,37 +55,26 @@ public class Code03_BiggestBSTTopologyInTree {
 	// t: 代表树 t[i][0]是i节点的父节点、t[i][1]是i节点的左孩子、t[i][2]是i节点的右孩子
 	// m: i节点为头的最大bst拓扑结构大小 -> m[i]
 	// 返回: 以h为头的整棵树上，最大bst拓扑结构的大小
-	public static int maxBSTTopology(int h, int[][] t, int[] m) {
+	public static int maxBSTTopology(int h) {
 		if (h == 0) {
 			return 0;
 		}
-		int l = t[h][1];
-		int r = t[h][2];
-		int c = 0;
-		int p1 = maxBSTTopology(l, t, m);
-		int p2 = maxBSTTopology(r, t, m);
-		while (l < h && m[l] != 0) {
-			l = t[l][2];
+		int l = tree[h][1];
+		int r = tree[h][2];
+		int p1 = maxBSTTopology(l);
+		int p2 = maxBSTTopology(r);
+		int tmp = l;
+		while (tmp < h && record[tmp] != 0) {
+			tmp = tree[tmp][2];
 		}
-		if (m[l] != 0) {
-			c = m[l];
-			while (l != h) {
-				m[l] -= c;
-				l = t[l][0];
-			}
-		}
-		while (r > h && m[r] != 0) {
-			r = t[r][1];
-		}
-		if (m[r] != 0) {
-			c = m[r];
-			while (r != h) {
-				m[r] -= c;
-				r = t[r][0];
-			}
+		record[l] -= record[tmp];
+		tmp = r;
+		while (tmp > h && record[tmp] != 0) {
+			tmp = tree[tmp][1];
 		}
-		m[h] = m[t[h][1]] + m[t[h][2]] + 1;
-		return Math.max(Math.max(p1, p2), m[h]);
+		record[r] -= record[tmp];
+		record[h] = record[l] + record[r] + 1;
+		return Math.max(Math.max(p1, p2), record[h]);
 	}
 
 }