Min Stack

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.

C：
#include<stdlib.h>
#include<stdio.h>


struct node
{
    int data;
    struct node* down;
};
typedef struct node node;


struct stack
{
    node* top;
    int size;
};
typedef struct stack Stack;


Stack* EmptyStack()
{
    Stack *top = (Stack*)malloc(sizeof(Stack*));
    if(top)
    {
        top->top = NULL;
        top->size = 0;
    }
    return top;
}


void push(Stack* stack,Stack* minstack,int x) {
    node* newtop=(node *)malloc(sizeof(node));
    newtop->data=x;
    newtop->down=stack->top;
    stack->top=newtop;
    stack->size++;
    if(minstack->top==NULL || x <= minstack->top->data){
        node* newmin=(node *)malloc(sizeof(node));
        newmin->data=x;
        newmin->down=minstack->top;
        minstack->top=newmin;
        minstack->size++;
    }
    return;
}


void pop(Stack* stack,Stack* minstack){
    node* p;
    int d;
    if(stack->top==NULL && stack->size==0) return;
    else{
        p=stack->top;
        d=stack->top->data;
        stack->top=stack->top->down;
        stack->size--;
        free(p);
        if(d == minstack->top->data){
            if(minstack->top == NULL && minstack->size == 0) return;
            else {
               p=minstack->top;
               minstack->top=minstack->top->down;
               stack->size--;
               free(p);
            }
        }
    }
    return;
}


int top(Stack* stack) {
    return stack->top->data;
}


int getMin(Stack* minstack){
    return minstack->top->data;
}


void main(){
    Stack* stack=EmptyStack();
    Stack* minstack=EmptyStack();
    int data;
    scanf("%d",&data);
    while(data>=0) {
        push(stack,minstack,data);
        scanf("%d",&data);
    }
    pop(stack,minstack);
    printf("%d\n",getMin(minstack));
}

C++
class MinStack {
private:
    stack<int> datastack;
    stack<int> minstack;
public:
    void push(int x) {
        datastack.push(x);
        if(minstack.empty() || x<=minstack.top())
            minstack.push(x);
    }

    void pop() {
        int data=datastack.top();
        datastack.pop();
        if(data==minstack.top()) minstack.pop();
    }

    int top() {
        return datastack.top();
    }

    int getMin() {
        return minstack.top();
    }
};

Min Stack

原文：http://blog.csdn.net/uj_mosquito/article/details/41944337