add 155

Author: luliyucoordinate

README.md

@@ -135,9 +135,10 @@ LeetCode
 |0131|[Palindrome Partitioning](https://leetcode.com/problems/palindrome-partitioning/) | c | [c++](./src/0131-Palindrome-Partitioning/0131.cpp) |[python](./src/0131-Palindrome-Partitioning/0131.py)|||Medium|
 |0132|[Palindrome Partitioning II](https://leetcode.com/problems/palindrome-partitioning/) | c | [c++](./src/0131-Palindrome-Partitioning/0131.cpp) |[python](./src/0131-Palindrome-Partitioning/0131.py)|||Medium|
 |0134|[Gas Station](https://leetcode.com/problems/gas-station/) | c | [c++](./src/0134-Gas-Station/0134.cpp) |[python](./src/0134-Gas-Station/0134.py)|||Medium|
-|0135|[Candy](https://leetcode.com/problems/gas-station/) | c | [c++](./src/0134-Gas-Station/0134.cpp) |[python](./src/0134-Gas-Station/0134.py)|||Medium|
+|0135|[Candy](https://leetcode.com/problems/gas-station/) | c | [c++](./src/0134-Gas-Station/0134.cpp) |[python](./src/0134-Gas-Station/0134.py)|||Hard|
 |0136|[Single Number](https://leetcode.com/problems/single-number/) | c | [c++](./src/0136-Single-Number/0136.cpp) |[python](./src/0136-Single-Number/0136.py)|||Easy|
 |0137|[Single Number II](https://leetcode.com/problems/single-number-ii/) | c | [c++](./src/0137-Single-Number-II/0137.cpp) |[python](./src/0137-Single-Number-II/0137.py)|||Medium|
+|0138|[Copy List with Random Pointer](https://leetcode.com/problems/single-number-ii/) | c | [c++](./src/0137-Single-Number-II/0137.cpp) |[python](./src/0137-Single-Number-II/0137.py)|||Medium|
 |0139|[Word Break](https://leetcode.com/problems/word-break/) | c | [c++](./src/0139-Word-Break/0139.cpp) |[python](./src/0139-Word-Break/0139.py)|||Medium|
 |0141|[Linked List Cycle](https://leetcode.com/problems/linked-list-cycle/) | c | [c++](./src/0141-Linked-List-Cycle/0141.cpp) |[python](./src/0141-Linked-List-Cycle/0141.py)|||Easy|
 |0142|[Linked List Cycle II](https://leetcode.com/problems/linked-list-cycle-ii/) | c | [c++](./src/0142-Linked-List-Cycle-II/0142.cpp) |[python](./src/0142-Linked-List-Cycle-II/0142.py)|||Medium|
@@ -152,6 +153,7 @@ LeetCode
 |0152|[Maximum Product Subarray](https://leetcode.com/problems/evaluate-reverse-polish-notation/) | c | [c++](./src/0152-Maximum-Product-Subarray/0152.cpp) |[python](./src/0152-Maximum-Product-Subarray/0152.py)|||Medium|
 |0153|[Find Minimum in Rotated Sorted Array](https://leetcode.com/problems/find-minimum-in-rotated-sorted-array/) | c | [c++](./src/0153-Find-Minimum-in-Rotated-Sorted-Array/0153.cpp) |[python](./src/0153-Find-Minimum-in-Rotated-Sorted-Array/0153.py)|||Medium|
 |0154|[Find Minimum in Rotated Sorted Array II](https://leetcode.com/problems/find-minimum-in-rotated-sorted-array-ii/) | c | [c++](./src/0154-Find-Minimum-in-Rotated-Sorted-Array-II/0154.cpp) |[python](./src/0154-Find-Minimum-in-Rotated-Sorted-Array-II/0154.py)|||Hard|
+|0155|[Min Stack](https://leetcode.com/problems/min-stack/) | c | [c++](./src/0155-Min-Stack/0155.cpp) |[python](./src/0155-Min-Stack/0155.py)|||Easy|
 |0162|[Find Peak Element](https://leetcode.com/problems/find-peak-element/) | c | [c++](./src/0162-Find-Peak-Element/0162.cpp) |[python](./src/0162-Find-Peak-Element/0162.py)|||Medium|
 |0167|[Two Sum II - Input array is sorted](https://leetcode.com/problems/two-sum-ii-input-array-is-sorted/) | c | [c++](./src/0167-Two-Sum-II-Input-array-is-sorted/0167.cpp) |[python](./src/0167-Two-Sum-II-Input-array-is-sorted/0167.py)|||Easy|
 |0169|[Majority Element](https://leetcode.com/problems/majority-element/) | c | [c++](./src/0169-Majority-Element/0169.cpp) |[python](./src/0169-Majority-Element/0169.py)|||Easy|

src/0155-Min-Stack/0155.cpp

@@ -0,0 +1,26 @@
+static int x = []() {std::ios::sync_with_stdio(false); cin.tie(0); return 0; }();
+class MinStack 
+{
+public:
+    void push(int x) 
+    {
+	    s1.push(x);
+	    if (s2.empty() || x <= getMin())  s2.push(x);	    
+    }
+    void pop() 
+    {
+	    if (s1.top() == getMin())  s2.pop();
+	    s1.pop();
+    }
+    int top() 
+    {
+	    return s1.top();
+    }
+    int getMin() 
+    {
+	    return s2.top();
+    }
+private:
+    stack<int> s1;
+    stack<int> s2;
+};

src/0155-Min-Stack/0155.py

@@ -0,0 +1,41 @@
+class MinStack:
+    def __init__(self):
+        """
+        initialize your data structure here.
+        """
+        self.data = [] 
+        self.min_val = float("inf")
+
+    def push(self, x):
+        """
+        :type x: int
+        :rtype: void
+        """
+        if x <= self.min_val:
+            self.data.append(self.min_val)
+            self.min_val = x
+            
+        self.data.append(x)
+
+    def pop(self):
+        """
+        :rtype: void
+        """
+        if self.data[-1] == self.min_val:
+            self.data.pop()
+            self.min_val = self.data[-1]
+            self.data.pop()
+        else:
+            self.data.pop()
+
+    def top(self):
+        """
+        :rtype: int
+        """
+        return self.data[-1]
+
+    def getMin(self):
+        """
+        :rtype: int
+        """
+        return self.min_val