modify code

体系学习班/class16/Code03_TopologicalOrderBFS1.java

@@ -6,7 +6,7 @@ import java.util.LinkedList;
 import java.util.Queue;
 
 // OJ链接：https://www.lintcode.com/problem/topological-sorting
-public class Code03_TopologicalOrderBFS {
+public class Code03_TopologicalOrderBFS1 {
 
 	// 不要提交这个类
 	public static class DirectedGraphNode {

体系学习班/class16/Code03_TopologicalOrderBFS2.java

@@ -0,0 +1,90 @@
+package class16;
+
+// 课上没讲这个实现
+// 因为是一样的，都是根据入度来求拓扑排序，只不过是牛客网的测试数据
+// 测试链接 : https://www.nowcoder.com/questionTerminal/88f7e156ca7d43a1a535f619cd3f495c
+// 请同学们务必参考如下代码中关于输入、输出的处理
+// 这是输入输出处理效率很高的写法
+// 提交以下所有代码，把主类名改成Main，可以直接通过
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.io.OutputStreamWriter;
+import java.io.PrintWriter;
+import java.io.StreamTokenizer;
+import java.util.ArrayList;
+import java.util.Arrays;
+
+public class Code03_TopologicalOrderBFS2 {
+
+	public static int MAXN = 200001;
+
+	public static int[] queue = new int[MAXN];
+
+	public static int[] indegree = new int[MAXN];
+
+	public static int[] ans = new int[MAXN];
+
+	public static int n, m, from, to;
+
+	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) {
+			n = (int) in.nval;
+			in.nextToken();
+			m = (int) in.nval;
+			ArrayList<ArrayList<Integer>> graph = new ArrayList<>();
+			for (int i = 0; i <= n; i++) {
+				graph.add(new ArrayList<>());
+			}
+			for (int i = 0; i < m; i++) {
+				in.nextToken();
+				from = (int) in.nval;
+				in.nextToken();
+				to = (int) in.nval;
+				graph.get(from).add(to);
+			}
+			if (!topoSort(graph)) {
+				out.println(-1);
+			} else {
+				for (int i = 0; i < n - 1; i++) {
+					out.print(ans[i] + " ");
+				}
+				out.println(ans[n - 1]);
+			}
+			out.flush();
+		}
+	}
+
+	// 有拓扑排序返回true
+	// 没有拓扑排序返回false
+	public static boolean topoSort(ArrayList<ArrayList<Integer>> graph) {
+		Arrays.fill(indegree, 1, n + 1, 0);
+		for (ArrayList<Integer> nexts : graph) {
+			for (int next : nexts) {
+				indegree[next]++;
+			}
+		}
+		int l = 0;
+		int r = 0;
+		for (int i = 1; i <= n; i++) {
+			if (indegree[i] == 0) {
+				queue[r++] = i;
+			}
+		}
+		int cnt = 0;
+		while (l < r) {
+			int cur = queue[l++];
+			ans[cnt++] = cur;
+			for (int next : graph.get(cur)) {
+				if (--indegree[next] == 0) {
+					queue[r++] = next;
+				}
+			}
+		}
+		return cnt == n;
+	}
+
+}