155-min-stack

155. Min Stack (Medium) (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 value) pushes the element value 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. Constraints: - -2^31 <= val <= 2^31 - 1 - Methods pop, top and getMin operations will always be called on non-empty stacks.
• At most 3 * 10^4 calls will be made to push, pop, top, and getMin. You must implement a solution with O(1) time complexity for each function.

class MinStack {
  private stack: number[] = [];
  private minStack: number[] = [];
 
  constructor() {}
 
  push(val: number): void {
    this.stack.push(val);
    const currentMin =
      this.minStack.length === 0 ? Infinity : this.minStack.at(-1)!;
    this.minStack.push(Math.min(val, currentMin));
  }
 
  pop(): void {
    this.stack.pop();
    this.minStack.pop();
  }
 
  top(): number {
    return this.stack.at(-1);
  }
 
  getMin(): number {
    return this.minStack.at(-1);
  }
}
 
 
// Local check:
const minStack = new MinStack();
minStack.push(1);
minStack.push(2);
minStack.push(0);
console.log(minStack.getMin());
minStack.pop();
console.log(minStack.top());
console.log(minStack.getMin());

Example 1:
 
    Input
    ["MinStack", "push", 1, "push", 2, "push", 0, "getMin", "pop", "top", "getMin"]
 
    Output
    [null,null,null,null,0,null,2,1]
 
    Explanation

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