[算法] 堆栈

顺序存储实现：

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

typedef int Position;
typedef int ElementType;
typedef struct SNode *PtrToSNode;
struct SNode {
    ElementType *Data;
    Position Top;
    int MaxSize;
};
typedef PtrToSNode Stack;
//创建
Stack CreateStack(int MaxSize) {
    Stack S=(Stack)malloc(sizeof(struct SNode));
    S->Data=(ElementType*)malloc(MaxSize * sizeof(ElementType));
    S->Top=-1;
    S->MaxSize=MaxSize;
    return S;
}
//入栈
bool IsFull(Stack S) {
    return(S->Top==S->MaxSize-1);
}
bool Push(Stack S,ElementType X) {
    if(IsFull(S)) {
        printf("堆栈满");
        return false;
    } else {
        S->Data[++(S->Top)]=X;
        return true;
    }
}
//出栈
bool IsEmpty(Stack S) {
    return(S->Top==-1);
}
ElementType Pop(Stack S) {
    if(IsEmpty(S)) {
        printf("堆栈空");
        return -1;
    } else
        return(S->Data[(S->Top)--]);
}

int main(){
    Stack st;
    st = CreateStack(3);
    Push(st,10);
    Push(st,20);
    Push(st,30);
    printf("%d",Pop(st));
    printf("%d",Pop(st));
    printf("%d",Pop(st));
}

分析：

1、定义结构体：数组Data[MaxSize]存储数据；Top记录栈顶元素下标；MaxSize记录堆栈容量

2、创建：为栈申请内存；根据容量为数据申请内存；初始化Top

3、入栈、出栈：都在栈顶完成；入栈判满，出栈判空；入栈先加，出栈后减

链式存储实现：

#include<stdio.h>
#include<stdlib.h>
typedef int ElementType;
typedef struct SNode *PtrToSNode;
struct SNode {
    ElementType Data;
    PtrToSNode Next;
};
typedef PtrToSNode Stack;
//创建 
Stack CreateStack() {
    Stack S;
    S=(Stack)malloc(sizeof(struct SNode));
    S->Next=NULL;
    return S;
}

bool IsEmpty(Stack S) {
    return(S->Next==NULL);
}
//压栈 
bool Push(Stack S,ElementType X){
    PtrToSNode TmpCell;
    TmpCell=(PtrToSNode)malloc(sizeof(struct SNode));
    TmpCell->Data=X;
    TmpCell->Next=S->Next;
    S->Next=TmpCell; 
    return true;
}
//出栈 
ElementType Pop(Stack S){
    PtrToSNode FirstCell;
    ElementType TopElem;
    if(IsEmpty(S)){
        printf("堆栈空");
        return -1; 
    }
    else{
        FirstCell=S->Next;
        TopElem=FirstCell->Data;
        S->Next=FirstCell->Next;
        free(FirstCell);
        return TopElem;
    }
}

int main() {
Stack st;
st = CreateStack();
Push(st,10);
Push(st,20);
Push(st,30);
printf("%d",Pop(st));
printf("%d",Pop(st));
printf("%d",Pop(st));
}