Added solution of problem 155

Author: kurpenok

src/solutions/mod.rs

@@ -89,6 +89,7 @@ pub mod s0150_evaluate_reverse_polish_notation;
 pub mod s0151_reverse_words_in_a_string;
 pub mod s0152_maximum_product_subarray;
 pub mod s0153_find_minimum_in_rotated_sorted_array;
+pub mod s0155_min_stack;
 pub mod s0231_power_of_two;
 pub mod s0232_implement_queue_using_stacks;
 pub mod s0234_palindrome_linked_list;

src/solutions/s0155_min_stack.rs

@@ -0,0 +1,57 @@
+use std::collections::VecDeque;
+
+pub struct MinStack {
+    minimum: i32,
+    stack: VecDeque<i32>,
+}
+
+impl MinStack {
+    pub fn new() -> Self {
+        MinStack {
+            minimum: i32::MAX,
+            stack: VecDeque::new(),
+        }
+    }
+
+    pub fn push(&mut self, val: i32) {
+        self.minimum = std::cmp::min(self.minimum, val);
+        self.stack.push_front(val);
+    }
+
+    pub fn pop(&mut self) {
+        self.stack.pop_front();
+        self.minimum = match self.stack.iter().min() {
+            Some(m) => *m,
+            None => i32::MAX,
+        }
+    }
+
+    pub fn top(&self) -> i32 {
+        *self.stack.front().unwrap()
+    }
+
+    pub fn get_min(&self) -> i32 {
+        self.minimum
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    #[test]
+    fn test_case_1() {
+        let mut stack = MinStack::new();
+
+        stack.push(-2);
+        stack.push(0);
+        stack.push(-3);
+
+        assert_eq!(stack.get_min(), -3);
+
+        stack.pop();
+
+        assert_eq!(stack.top(), 0);
+        assert_eq!(stack.get_min(), -2);
+    }
+}