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--- java_primer [2020/08/18 16:33] – [Queue] jrseti
+++ java_primer [2020/11/19 17:19] (current) – [LinkedHashMap] jrseti
@@ Line 17: / Line 17: @@
   * But, **keys are ordered**!
   * No null keys
+  * keySet()and values() return in ascending order
 ====LinkedHashMap====
+**An OrderedDict!**
 Same as hashMap but preserves **insertion order**. O(1) insertion and lookup.
@@ Line 105: / Line 108: @@
 =====Stacks=====
-<code>import java.util.*</code>
+<code>import java.util.*
+Stack<Integer> stack = new Stack<>();;
+</code>
 pop(), peek(), push(), empty(), search()
@@ Line 117: / Line 122: @@
 </code>
-=====PriorityQueue=====
 =====PriorityQueue=====
 https://www.geeksforgeeks.org/priority-queue-class-in-java-2/
+poll(), remove(), add()
+<code>
+class The_Comparator implements Comparator<String> {
+    public int compare(String str1, String str2)
+    {
+        String first_Str;
+        String second_Str;
+        first_Str = str1;
+        second_Str = str2;
+        return second_Str.compareTo(first_Str);
+    }
+}
+PriorityQueue<String> queue = new PriorityQueue<String>(new The_Comparator());
+</code>
 =====DFS=====
@@ Line 142: / Line 164: @@
   * LinkedList is better with add(), remove.
   * ArrayList better with get(), set().
+  * Char to digit: s.charAt(num2Idx) - '0'
+=====TRICKS=====
+====Log and division====
+  * a / b = Math.exp(Math.log(a) - Math.log(b))
+====Random====
+<code>
+//Random number from 0 to 5
+Random rand = new Random();
+int r = rand.nextInt(6);
+</code>
+or
+<code>
+//Number between 0.0 and 1.0;
+Math.random();
+</code>