栈

• 栈概念

栈（stack）又名堆栈，它是一种运算受限的线性表。限定仅在表尾进行插入和删除操作的线性表。这一端被称为栈顶，相对地，把另一端称为栈底。向一个栈插入新元素又称作进栈、入栈或压栈，它是把新元素放到栈顶元素的上面，使之成为新的栈顶元素；从一个栈删除元素又称作出栈或退栈，它是把栈顶元素删除掉，使其相邻的元素成为新的栈顶元素。

• 栈特点

  运算受限的线性表：表现为栈顶入栈、栈顶出栈，先进后出

• 栈的顺序存储实现

  1. 顺序栈示意图

     

  2. 初始化

  #define OK 1
  #define ERROR 0
  #define TRUE 1
  #define FALSE 0
  #define MAXSIZE 10
  
  typedef int ElemType;
  typedef int Status;
  typedef struct{
      ElemType *data;
      int top;  //用来记录栈顶位置
  }Stack;
  
  Status creatStack(Stack *S){
      if(S->data == NULL){
      S->data = (ElemType *)malloc(sizeof(ElemType) * MAXSIZE);
      if(!S->data) exit(0);
      S->top = -1; //默认当top=-1时为空栈
  }
  return OK;
  }
  

  2. 入栈

     

  //入栈
  //1.先判断当前栈是否已满（满栈不能入栈）
  //2.赋值data[top+1] = data
  //3.top+1
  Status pushData(Stack *S,ElemType data){
      if(S->data == NULL) return ERROR;
      if(S->top + 1 > MAXSIZE -1) return ERROR;
      S->data[S->top + 1] = data;
      S->top ++;
      return OK;
  }
  

  3. 出栈

     

  //出栈
  //只需要将top减一即可
  Status popData(Stack *S){
      if(S->data == NULL) return ERROR;
      if(S->top == -1) return ERROR;
      S->top --;
      
      return OK;
  }
  

  4. 置空、获取栈长度、遍历

  //清空 只需将top置成-1即可
  Status cleanStack(Stack *S){
      if(S->data == NULL) return ERROR;
      S->top = -1;
      return OK;
  }
  
  //获取栈的长度
  Status getLength(Stack S,int *length){
      if(S.data == NULL) return ERROR;
      *length = S.top + 1;
      return OK;
  }
  
  //遍历栈
  void traverseStack(Stack S){
      for(int i = 0; i <= S.top; i ++){
          printf("%d ",S.data[i]);
      }
      printf("\n");
  }
  

• 栈的链式存储实现

  1. 链式栈示意图

     

  2. 初始化

  #define OK 1
  #define ERROR 0
  #define TRUE 1
  #define FALSE 0
  
  typedef int ElemType;
  typedef int Status;
  typedef struct StackNode{
      ElemType data;
      struct StackNode *next;
  }StackNode,*StackPtr;
  
  typedef struct {
      StackPtr top;
      int length;
  } Stack;
  
  //初始化
  Status creatStack(Stack *S){
      S->top = NULL;
      S->length = 0;
      return OK;
  }
  

  3. 入栈

     

  //入栈
  Status pushData(Stack *S, ElemType data){
      if(!S) return ERROR;
      StackPtr temp = (StackPtr)malloc(sizeof(StackPtr));
      if(!temp) exit(0);
      temp->next = S->top;
      temp->data = data;
      S->top = temp;
      S->length ++;
      return OK;
  }
  

  4. 出栈

     

  //出栈
  Status popData(Stack *S){
      if(!S) return ERROR;
      if(S->length == 0) return OK;
      StackPtr temp = S->top;
      S->top = temp->next;
      S->length --;
      free(temp);
      return OK;
  }
  

  5. 遍历

  //遍历
  void traverse(Stack S){
      while (S.top) {
          printf("%d ",S.top->data);
          S.top = S.top->next;
      }
      printf("\n");
  }