feat: add more

Author: gengjiawen

stack/_0155_min_stack.rs

@@ -0,0 +1,99 @@
+// https://leetcode.com/problems/min-stack
+//
+// Design a stack that supports push, pop, top, and retrieving the minimum element in constant time.
+//
+// Implement the `MinStack` class:
+//
+// *   `MinStack()` initializes the stack object.
+// *   `void push(int val)` pushes the element `val` onto the stack.
+// *   `void pop()` removes the element on the top of the stack.
+// *   `int top()` gets the top element of the stack.
+// *   `int getMin()` retrieves the minimum element in the stack.
+//
+// **Example 1:**
+//
+// ```
+// **Input**
+// ["MinStack","push","push","push","getMin","pop","top","getMin"]
+// [[],[-2],[0],[-3],[],[],[],[]]
+//
+// **Output**
+// [null,null,null,null,-3,null,0,-2]
+//
+// **Explanation**
+// MinStack minStack = new MinStack();
+// minStack.push(-2);
+// minStack.push(0);
+// minStack.push(-3);
+// minStack.getMin(); // return -3
+// minStack.pop();
+// minStack.top();    // return 0
+// minStack.getMin(); // return -2
+// ```
+//
+// **Constraints:**
+//
+// *   `-2<sup>31</sup> <= val <= 2<sup>31</sup> - 1`
+// *   Methods `pop`, `top` and `getMin` operations will always be called on **non-empty** stacks.
+// *   At most `3 * 10<sup>4</sup>` calls will be made to `push`, `pop`, `top`, and `getMin`.
+
+struct MinStack {
+    data: Vec<i32>,
+    min: i32,
+}
+
+impl MinStack {
+    fn new() -> Self {
+        MinStack {
+            data: Vec::new(),
+            min: std::i32::MAX,
+        }
+    }
+
+    fn push(&mut self, val: i32) {
+        self.data.push(val);
+        if self.min > val {
+            self.min = val;
+        }
+    }
+
+    fn pop(&mut self) {
+        let pop = self.data.pop().unwrap();
+        if pop == self.min {
+            if !(self.data.is_empty()) {
+                self.min = *self.data.iter().min().unwrap();
+            } else {
+                self.min = std::i32::MAX;
+            }
+        }
+    }
+
+    fn top(&self) -> i32 {
+        *self.data.last().unwrap()
+    }
+
+    fn get_min(&self) -> i32 {
+        return self.min;
+    }
+}
+
+/**
+ * Your MinStack object will be instantiated and called as such:
+ * let obj = MinStack::new();
+ * obj.push(val);
+ * obj.pop();
+ * let ret_3: i32 = obj.top();
+ * let ret_4: i32 = obj.get_min();
+ */
+
+#[test]
+pub fn t1() {
+    let mut obj = MinStack::new();
+    obj.push(-2);
+    obj.push(0);
+    obj.push(-3);
+    assert_eq!(obj.get_min(), -3);
+    obj.pop();
+    assert_eq!(obj.top(), 0);
+    assert_eq!(obj.get_min(), -2);
+}

stack/lib.rs

@@ -1,4 +1,5 @@
 #![allow(dead_code)]
 
 mod _0020_valid_parentheses;
+mod _0155_min_stack;
 mod _1598_crawler_log_folder;