feat: dijkstra

Author: haotf

Diff for: 743.网络延迟时间.java

@@ -1,3 +1,10 @@
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Map;
+import java.util.PriorityQueue;
+
 /*
  * @lc app=leetcode.cn id=743 lang=java
  *
@@ -6,9 +13,63 @@
 
 // @lc code=start
 class Solution {
+    public static List<int[]>[] graph;
+
     public int networkDelayTime(int[][] times, int n, int k) {
+        buildGraph(times, n);
+        int[] distToTarget = new int[n + 1];
+        Arrays.fill(distToTarget, Integer.MAX_VALUE);
+        distToTarget[k] = 0;
+
+        PriorityQueue<State> pq = new PriorityQueue<State>((a, b) -> a.distFromStart - b.distFromStart);
+        pq.add(new State(k, 0));
+
+        while (!pq.isEmpty()) {
+            State state = pq.poll();
+            if (state.distFromStart > distToTarget[state.id])
+                continue;
+            List<int[]> targets = graph[state.id];
+            for (int[] target : targets) {
+                int t = target[0];
+                int w = target[1];
+                int distFromStart = w + state.distFromStart;
+                if (distToTarget[t] > distFromStart) {
+                    distToTarget[t] = distFromStart;
+                    pq.offer(new State(t, distFromStart));
+                }
+            }
+        }
+        int max = 0;
+        for (int i = 1; i < distToTarget.length; i++) {
+            max = Math.max(max, distToTarget[i]);
+        }
+
+        return max == Integer.MAX_VALUE ? -1 : max;
+
+    }
 
+    private static void buildGraph(int[][] times, int n) {
+        List<int[]>[] list = new LinkedList[n + 1];
+        for (int i = 0; i < list.length; i++) {
+            list[i] = new LinkedList<>();
+        }
+        for (int[] g : times) {
+            int from = g[0];
+            int to = g[1];
+            int weight = g[2];
+            list[from].add(new int[] { to, weight });
+        }
+        graph = list;
     }
 }
-// @lc code=end
 
+class State {
+    public int id;
+    public int distFromStart;
+
+    public State(int id, int distFromStart) {
+        this.id = id;
+        this.distFromStart = distFromStart;
+    }
+}
+// @lc code=end

Diff for: 817.链表组件.java

@@ -0,0 +1,47 @@
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+import java.util.stream.Collectors;
+
+/*
+ * @lc app=leetcode.cn id=817 lang=java
+ *
+ * [817] 链表组件
+ */
+
+// @lc code=start
+/**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ * int val;
+ * ListNode next;
+ * ListNode() {}
+ * ListNode(int val) { this.val = val; }
+ * ListNode(int val, ListNode next) { this.val = val; this.next = next; }
+ * }
+ */
+class Solution {
+    public int numComponents(ListNode head, int[] nums) {
+        Set<Integer> set = new HashSet<>(Arrays.stream(nums).boxed().collect(Collectors.toList()));
+        int res = 0;
+        ListNode p = head;
+
+        boolean start = false;
+        while (p != null) {
+            if (set.contains(p.val)) {
+                if (start == false) {
+                    start = true;
+                    res++;
+                }
+            } else {
+                start = false;
+            }
+            p = p.next;
+        }
+
+        return res;
+    }
+}
+// @lc code=end