Design stack containing min function

//设计包含Min函数的栈
//定义栈的数据结构，要求添加一个函数，能够得到栈的最小元素。要求函数Min, push，pop的时间复杂度都是O(1).
#include <iostream>
#include <cstdlib>
struct minStackElement{
    int data;
    int min;
};
struct minStack{
    minStackElement *data;
    int size;
    int top;
};
minStack *minStackInit(int maxSize){
    minStack *stack;
    stack->size=maxSize;
    stack->data=(minStackElement*)malloc(sizeof(minStackElement)*maxSize);
    stack->top=0;
    return stack;
}
void minStackFree(minStack stack){
    free(stack.data);
}
void minStackPush(minStack *stack,int d){
    if(stack->top==stack->size){
        std::cout<<"out of stack space.";
        }
        minStackElement *p=stack->data+stack->top;
        p->data=d;
        p->min=(stack->top==0?d:(stack->data+(stack->top-1))->min);
        if(p->min>d)p->min=d;
        stack->top++;
}

int minStackPop(minStack *stack){
    if(stack->top==0)
    std::cout<<"stack is empty";
    int po= (stack->data+stack->top)->data;
    stack->top--;
    return po;
}

int minStackMin(minStack *stack){
    if(stack->top==0)
    std::cout<<"stack is empty";
    return (stack->data+stack->top-1)->min;
}

int main(){
    minStack *stack=minStackInit(5);
    minStackPush(stack,5);
    minStackPush(stack,6);
    minStackPush(stack,10);
    minStackPush(stack,7);
    int mini=minStackMin(stack);
    std::cout<<mini;
    std::cin>>mini;
}
//PS:摘自某公司招聘题目，学习中，不喜随便喷