create day 42 problem

2021-08/2021-08-26 (day39)/README.md

@@ -1,12 +1,12 @@
-# 70. Climbing Stairs
+**# 70. Climbing Stairs
 
 `Easy`
 
 ## Description
 
 <p>You are climbing a staircase. It takes <code>n</code> steps to reach the top.</p>
 
-<p>Each time you can either climb <code>1</code> or <code>2</code> steps. In how many distinct ways can you climb to the top?</p>
+<p>Each time you can either climb <code>1</code> or <code>2</code> steps. In how many distinct ways can you climb to the top?</p>**
 
 <p>&nbsp;</p>
 <p><strong>Example 1:</strong></p>

2021-08/2021-08-28 (day41)/AGO/solution.ts

@@ -14,3 +14,4 @@ function canJump(nums: number[]): boolean {
     }  
     return zeroIndex == -1;
 };
+

2021-08/2021-08-29 (day42)/README.md

@@ -0,0 +1,26 @@
+# Day 42 Binary Heap
+
+Extend and implement a bianry heap class below.
+
+```ts
+abstract class BinaryHeap{
+    // type: true is max heap, false is min heap
+    // default min heap
+    constructor(heap:number[], type?: bool = false);
+
+    private heap: number[]; // store value inside heap
+    private type: bool;
+    private heapify(): void; // sort heap
+
+    public IsEmpty(): bool; // if heap is empty, return true
+    public root(): number; // return value of root
+    public pop(): number; // pop root value and remove from heap
+    public push(value: number); // insert a value into heap and call heapify to sort
+}
+```
+
+Here is some introduction
+
+http://alrightchiu.github.io/SecondRound/priority-queuebinary-heap.html
+
+https://medium.com/@Kadai/%E8%B3%87%E6%96%99%E7%B5%90%E6%A7%8B%E5%A4%A7%E4%BE%BF%E7%95%B6-binary-heap-ec47ca7aebac

README.md

@@ -50,7 +50,7 @@
 | 039 | [70][0070] | [Climbing Stairs](<./2021-08/2021-08-26%20(day39)>) | ![Easy][Easy] | Math; Dynamic Programming; Memoization | 
 | 040 | [747][0747] | [Min Cost Climbing Stairs](<./2021-08/2021-08-27%20(day40)>) | ![Easy][Easy] | Array; Dynamic Programming | 
 | 041 | [55][0055] | [Jump Game](<./2021-08/2021-08-28%20(day41)>) | ![Medium][Medium] | Array; Dynamic Programming; Greedy | 
-
+| 042 |   | [Binary Heap](<./2021-08/2021-08-29%20(day42)>) | ![Medium][Medium] | Heap; Priority Queue; | 
 
 
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