Problem
Design a stack that supports push, pop, top, and retrieving the minimum element in constant time.
- push(x) -- Push element x onto stack.
- pop() -- Removes the element on top of the stack.
- top() -- Get the top element.
- getMin() -- Retrieve the minimum element in the stack.
Example
MinStack minStack = new MinStack();
minStack.push(-2);
minStack.push(0);
minStack.push(-3);
minStack.getMin(); --> Returns -3.
minStack.pop();
minStack.top(); --> Returns 0.
minStack.getMin(); --> Returns -2.
Code
static int var = [](){
std::ios::sync_with_stdio(false);
cin.tie(NULL);
return 0;
}();
class MinStack {
public:
/** initialize your data structure here. */
vector<int> stack;
vector<int> minstack;
MinStack() {
}
void push(int x) {
stack.push_back(x);
if(!stack.empty() && (minstack.empty() || x<=minstack.back())){
minstack.push_back(x);
}
}
void pop() {
if(stack.back()==minstack.back())
minstack.pop_back();
stack.pop_back();
}
int top() {
return stack.back();
}
int getMin() {
return minstack.back();
}
};
/**
* Your MinStack object will be instantiated and called as such:
* MinStack obj = new MinStack();
* obj.push(x);
* obj.pop();
* int param_3 = obj.top();
* int param_4 = obj.getMin();
*/
Result
155. Min Stack.png
