modify code

MCA算法突击课/第03期/mca_07/Code04_NetworkDelayTime.java

@@ -32,7 +32,9 @@ public class Code04_NetworkDelayTime {
 			num++;
 			max = Math.max(max, delay);
 			for (int[] next : nexts.get(cur)) {
-				heap.add(new int[] { next[0], delay + next[1] });
+				if (!used[next[0]]) {
+					heap.add(new int[] { next[0], delay + next[1] });
+				}
 			}
 		}
 		return num < n ? -1 : max;

MCA算法突击课/第03期/mca_07/Test.java

@@ -0,0 +1,136 @@
+package 第03期.mca_07;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.PriorityQueue;
+
+public class Test {
+
+	// n : 1~n, 0~n-1
+	// edges(无向的！) : [1,5]
+	// [4,8]
+	// [3,7]
+	// 5 9 X
+	// 有向，带权重 : [1,5,10]
+	public static ArrayList<ArrayList<Integer>> createGraph(int n, int[][] edges) {
+		ArrayList<ArrayList<Integer>> graph = new ArrayList<>();
+		// 点的编号，1~n
+		for (int i = 0; i <= n; i++) {
+			graph.add(new ArrayList<>());
+		}
+		for (int[] e : edges) {
+			int from = e[0];
+			int to = e[1];
+			graph.get(from).add(to);
+		}
+		return graph;
+	}
+
+	public static List<Integer> topoSort(int n, ArrayList<ArrayList<Integer>> graph) {
+		// 点的编号，1~n
+		int[] inCnts = new int[n + 1];
+		for (int i = 1; i <= n; i++) {
+			ArrayList<Integer> inexts = graph.get(i);
+			for (int next : inexts) {
+				inCnts[next]++;
+			}
+		}
+		int[] queue = new int[n + 1];
+		int l = 0;
+		int r = 0;
+		// 谁入度为0，加入到queue里去！
+		for (int i = 1; i <= n; i++) {
+			if (inCnts[i] == 0) {
+				queue[r++] = i;
+			}
+		}
+		List<Integer> ans = new ArrayList<>();
+		while (l < r) { // 如果队列里还有东西，就继续
+			// cur就是当前弹出的点
+			int cur = queue[l++];
+			// 消除掉cur的影响！
+			for (int curNext : graph.get(cur)) {
+				if (--inCnts[curNext] == 0) {
+					queue[r++] = curNext;
+				}
+			}
+			ans.add(cur);
+		}
+		if (ans.size() != n) {
+			return null;
+		}
+		return ans;
+	}
+
+	// edges [3,5,10]
+	public static int kruskal(int n, int[][] edges) {
+		// 建图？没必要！
+		Arrays.sort(edges, (a, b) -> a[2] - b[2]);
+		UnionFind uf = new UnionFind(n);
+//		List<int[]> ans = 
+		int ans = 0;
+		for (int[] edge : edges) {
+			int a = edge[0];
+			int b = edge[1];
+			int weight = edge[2];
+			if (!uf.isSameSet(a, b)) {
+				ans += weight;
+				uf.union(a, b);
+			}
+		}
+		return ans;
+	}
+
+	public static class UnionFind {
+
+		public UnionFind(int n) {
+			// n 0 ~ n-1
+			// 1 ~ n
+
+		}
+
+		public boolean isSameSet(int a, int b) {
+			return true;
+		}
+
+		public void union(int a, int b) {
+
+		}
+
+	}
+
+	// n : 1 ~ n
+	// start : 源出发点
+	// graph : 整个图
+	public static int[] dij(int n, int start, ArrayList<ArrayList<int[]>> graph) {
+		int[] distance = new int[n + 1];
+		// distance[0] : start -> 0 0不存在，所以该空间不用！
+		// distance[1] : start -> 1 最短距离
+		// distance[i] : start -> i 最短距离
+
+		Arrays.fill(distance, -1);
+		// distance[i] = -1, -1代表，start -> i 记录没求过！
+		// [点号，cost]
+		PriorityQueue<int[]> heap = new PriorityQueue<>((a, b) -> a[1] - b[1]);
+		// start -> start 0
+		heap.add(new int[] { start, 0 });
+		while (!heap.isEmpty()) {
+			int[] cur = heap.poll();
+			int i = cur[0];
+			int cost = cur[1];
+			if (distance[i] == -1) { // 当前点之前没有弹出过！才处理!
+				distance[i] = cost;
+				for (int[] edge : graph.get(i)) {
+					int next = edge[0];
+					int weight = edge[1];
+					if (distance[next] != -1) {
+						heap.add(new int[] { next, cost + weight });
+					}
+				}
+			}
+		}
+		return distance;
+	}
+
+}

体系学习班/class16/Code06_NetworkDelayTime.java

@@ -34,7 +34,9 @@ public class Code06_NetworkDelayTime {
 			num++;
 			max = Math.max(max, delay);
 			for (int[] next : nexts.get(cur)) {
-				heap.add(new int[] { next[0], delay + next[1] });
+				if (!used[next[0]]) {
+					heap.add(new int[] { next[0], delay + next[1] });
+				}
 			}
 		}
 		return num < n ? -1 : max;