最小栈

链接：

https://leetcode-cn.com/problems/min-stack/description/

问题描述：

设计思路：

利用两个栈，一个正常出入数据，一个存储更新最小数据。

typedef struct {
    int* pst;
    int stTop;
    
    int* pminST;
    int minSTTop;
} MinStack;

/** initialize your data structure here. */
MinStack* minStackCreate(int maxSize) {
    MinStack* pst = (MinStack*)malloc(sizeof(MinStack));
    pst->pst = (int*)malloc(sizeof(int)*(maxSize));
    pst->stTop = 0;
    
    pst->pminST = (int*)malloc(sizeof(int)*(maxSize));
    pst->minSTTop = 0;
    
    return pst;
}

void minStackPush(MinStack* obj, int x) {
    int* pst = obj->pst;
    int* pminST = obj->pminST;
    
    pst[obj->stTop++] = x;
    if(obj->minSTTop == 0 
       || x <= pminST[obj->minSTTop-1])
    {
       pminST[obj->minSTTop++] = x; 
    }
}

void minStackPop(MinStack* obj) {
    int* pst = obj->pst;
    int* pminST = obj->pminST;
    if(pst[obj->stTop-1] == pminST[obj->minSTTop-1])
    {
        --obj->minSTTop;
    }
    
    --obj->stTop;
}

int minStackTop(MinStack* obj) {
    return obj->pst[obj->stTop-1];
}

int minStackGetMin(MinStack* obj) {
    return obj->pminST[obj->minSTTop-1];
}

void minStackFree(MinStack* obj) {
    free(obj->pst);
    free(obj->pminST);
    free(obj);
}

/**
 * Your MinStack struct will be instantiated and called as such:
 * struct MinStack* obj = minStackCreate(maxSize);
 * minStackPush(obj, x);
 * minStackPop(obj);
 * int param_3 = minStackTop(obj);
 * int param_4 = minStackGetMin(obj);
 * minStackFree(obj);
 */