第十一周学习知识总结

一、栈

1. 入栈

   void push(Stack *S, ElemType e) {
     S->elem[++S->top] = e; 
     if (S->top>=S->capacity) { 
       S->elem = (ElemType *) realloc(S->elem,
                                     (S->capacity+SEGMENT)*sizeof(ElemType));
       S->capacity += SEGMENT; 
      }
   }

    

2. 出栈

   ElemType pop(Stack *S) {
     ElemType e; 
       
     if (S->top<0) return -1; 
     e = S->elem[S->top--]; 
     if (S->top<=S->capacity-SEGMENT*2) {
    
       S->elem = (ElemType *) realloc(S->elem,
                                                          (S->capacity-SEGMENT)*sizeof(ElemType));
       S->capacity -= SEGMENT;                         
     }
     return e;
   }

二、栈的应用——括号匹配问题

// 检查字符串 str 是否全部是全括号 '(', ')', '[', ']', '{', 或 '}'。 
int allParenthesis(char *str) {
  int i;
  for (i=0; i<strlen(str); i++) 
    if (!(str[i]=='(' || str[i]==')' ||  
          str[i]=='[' || str[i]==']' ||
          str[i]=='{' || str[i]=='}')) return 0;

  return 1;  
}

// 检查两个字符是否匹配。
int isMatching(char e, char c) {

  return (e=='(' && c==')') || (e=='[' && c==']') || (e=='{' && c=='}'); } 


int parenthesisMatching(char *str) {  
  Stack S;
  char e; 
  int matching = 1; 
  int i; 
  initial(&S);
    
  for (i=0; i<strlen(str) && matching; i++) {    
    if (str[i]=='(' || str[i]=='[' || str[i]=='{') 
      push(&S, str[i]); 
    else {
      e = pop(&S); 
   
      if (!isMatching(e, str[i])) matching = 0;  
    } 
  }
  if (matching==1 && is_empty(S)) matching = 1; 
  else matching = 0;  
 clear(&S); 
  return matching; 
}