From 2a1004a7c7fc2bf58d381ea5fcc8630cc95dd5dc Mon Sep 17 00:00:00 2001
From: juan <juancloudcomputing@protonmail.com>
Date: Wed, 21 Sep 2022 14:35:34 +0800
Subject: [PATCH] vault backup: 2022-09-21 14:35:34

---
 OJ notes/pages/Leetcode Combinations.md       | 33 ++++++++++++++++++-
 .../Leetcode Implement-Queue-Using-Stacks.md  |  8 +++--
 2 files changed, 38 insertions(+), 3 deletions(-)

diff --git a/OJ notes/pages/Leetcode Combinations.md b/OJ notes/pages/Leetcode Combinations.md
index 2b751bb..2c0b30d 100644
--- a/OJ notes/pages/Leetcode Combinations.md	
+++ b/OJ notes/pages/Leetcode Combinations.md	
@@ -16,7 +16,7 @@
 >
 > ##### Revisions:
 >
-> N/A
+> 2022-09-21
 
 ##### Related topics:
 
@@ -110,3 +110,34 @@ public:
   }
 };
 ```
+
+Alternative solution using private values
+```cpp
+class Solution {
+  vector<vector<int>> ans;
+  vector<int> combs = {};
+  int N, K;
+  void backtrack(int cur) {
+    if (combs.size() == K) {
+      // we reached the end, should push to the answer array
+      ans.push_back(combs);
+      return;
+    } else if (cur <= N) {
+      combs.push_back(cur);
+      backtrack(cur + 1);
+
+      combs.pop_back();
+      backtrack(cur + 1);
+    }
+  }
+
+public:
+  vector<vector<int>> combine(int n, int k) {
+    N = n;
+    K = k;
+    backtrack(1);
+
+    return ans;
+  }
+};
+```
diff --git a/OJ notes/pages/Leetcode Implement-Queue-Using-Stacks.md b/OJ notes/pages/Leetcode Implement-Queue-Using-Stacks.md
index 8baa81c..50b65a0 100644
--- a/OJ notes/pages/Leetcode Implement-Queue-Using-Stacks.md	
+++ b/OJ notes/pages/Leetcode Implement-Queue-Using-Stacks.md	
@@ -16,13 +16,13 @@
 >
 > ##### Revisions:
 >
-> N/A
+> 2022-09-21
 
 ##### Related topics:
 
 ##### Links:
 
-- [Link to problem](https://leetcode.com/problems/implement-queue-using-stacks/submissions/)
+- [Link to problem](https://leetcode.com/problems/implement-queue-using-stacks/)
 
 ---
 
@@ -52,15 +52,19 @@ Implement the `MyQueue` class:
 ```
 
 **Output**
+```
 [null, null, null, 1, 1, false]
+```
 
 **Explanation**
+```
 MyQueue myQueue = new MyQueue();
 myQueue.push(1); // queue is: [1]
 myQueue.push(2); // queue is: [1, 2] (leftmost is front of the queue)
 myQueue.peek(); // return 1
 myQueue.pop(); // return 1, queue is [2]
 myQueue.empty(); // return false
+```
 
 #### Constraints