有效的括号 题目链接

// 栈结构
typedef char valuetype;
typedef struct {
	valuetype* arr;
	int top;
	int capacity;
} Stack;

void Init(Stack* stack);

void Push(Stack* stack, valuetype value);
void Pop(Stack* stack);

valuetype Top(Stack* stack);
int Size(Stack* stack);
bool Empty(Stack* stack);

void Destroy(Stack* stack);


bool isValid(char* s) {
	Stack stack;
	Init(&stack);

	while (*s) {
		if (*s == '(' || *s == '[' || *s == '{') {
			Push(&stack, *s); // 1.左括号入栈；
		}
		else { // 2.比较。
			if (Empty(&stack)) { // 2.1右括号比左括号多
				Destroy(&stack);
				return false;
			}
			else { // 2.2 比较左括号与右括号是否匹配
				char ch = Top(&stack);
				Pop(&stack);
				if ((ch == '(' && *s != ')') ||
					(ch == '[' && *s != ']') ||
					(ch == '{' && *s != '}')) {
					Destroy(&stack);
					return false;
				}
			}
		}
		s++;
	}
	// 如果栈里还剩有括号，说明左右括号没有对应
	bool res = Empty(&stack);
	Destroy(&stack);
	return res;
}


void Init(Stack* stack) {
	assert(stack);
	stack->arr = NULL;
	stack->capacity = stack->top = 0;
}

void Push(Stack* stack, valuetype value) {
	assert(stack);
	if (stack->top == stack->capacity) {
		stack->capacity = stack->capacity == 0 ? 10 : (int)(stack->capacity * 1.5);
		stack->arr = (valuetype*)realloc(stack->arr, sizeof(valuetype) * stack->capacity);
		if (stack->arr == NULL) {
			perror("realloc failed in the function Push(Stack*, valuetype).");
			return;
		}
	}
	stack->arr[stack->top++] = value;
}

void Pop(Stack* stack) {
	assert(stack && stack->top > 0);
	stack->top--;
}

valuetype Top(Stack* stack) {
	assert(stack && stack->top > 0);
	return stack->arr[stack->top - 1];
}

int Size(Stack* stack) {
	assert(stack);
	return stack->top;
}

bool Empty(Stack* stack) {
	assert(stack);
	return stack->top == 0;
}

void Destroy(Stack* stack) {
	assert(stack);
	free(stack->arr);
	stack->arr = NULL;
	stack->capacity = stack->top = 0;
}