(Leet Code c++)Min Stack

155. 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(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:

• -231 <= val <= 231 - 1
• Methods pop, top and getMin operations will always be called on non-empty stacks.
• At most 3 * 104 calls will be made to push, pop, top, and getMin.

Class로 min stack 구현.

 

class MinStack {
public:
    /** initialize your data structure here. */
    int data[100000];
    int index;
    
    MinStack() {
        index = 0;
    }
    
    void push(int val) {
        data[index++] = val;
    }
    
    void pop() {
        index--;
    }
    
    int top() {
        return data[index - 1];
    }
    
    int getMin() {
        int res = INT_MAX;
        
        for(int i = 0; i < index; i++){
            res = min(res, data[i]);
        }
        
        return res;
    }
};

/**
 * Your MinStack object will be instantiated and called as such:
 * MinStack* obj = new MinStack();
 * obj->push(val);
 * obj->pop();
 * int param_3 = obj->top();
 * int param_4 = obj->getMin();
 */