[ADD] LeetCode 155 MinStack

- Medium

Author: tdm1223

LeetCode/README.md

@@ -7,6 +7,6 @@
 |:----:|:-------------------------------------------------------------------:|:----------------------------------:|:----:|:--------------------------------------------------------------------------------:|:---------------------------------------:|
 |  1   |           [TwoSum](https://leetcode.com/problems/two-sum)           |      [cpp](source/TwoSum.cpp)      |  2   |       [PalindromeNumber](https://leetcode.com/problems/palindrome-number)        |   [cpp](source/PalindromeNumber.cpp)    |
 |  3   | [ValidParentheses](https://leetcode.com/problems/valid-parentheses) | [cpp](source/ValidParentheses.cpp) |  4   | [MiddleOfTheLinkedList](https://leetcode.com/problems/middle-of-the-linked-list) | [cpp](source/MiddleOfTheLinkedList.cpp) |
-|  5   |          [PlusOne](https://leetcode.com/problems/plus-one)          |     [cpp](source/PlusOne.cpp)      |      |                                                                                  |                                         |
+|  5   |          [PlusOne](https://leetcode.com/problems/plus-one)          |     [cpp](source/PlusOne.cpp)      |  6   |               [MinStack](https://leetcode.com/problems/min-stack)                | [cpp](source/MiddleOfTheLinkedList.cpp) |
 
 </details>

LeetCode/source/MinStack.cpp

@@ -0,0 +1,42 @@
+// PalindromeNumber
+// 2022.08.10
+// Medium
+class MinStack
+{
+public:
+    stack<int> st;
+    stack<int> minSt;
+
+    void push(int val)
+    {
+        st.push(val);
+        if (minSt.size() == 0)
+        {
+            minSt.push(val);
+        }
+        else if (val <= minSt.top())
+        {
+            minSt.push(val);
+        }
+    }
+
+    void pop()
+    {
+        int top = st.top();
+        if (top == minSt.top())
+        {
+            minSt.pop();
+        }
+        st.pop();
+    }
+
+    int top()
+    {
+        return st.top();
+    }
+
+    int getMin()
+    {
+        return minSt.top();
+    }
+};