【有效的括号】

题目

1、左括号入栈
2、右括号出栈顶括号进行匹配

栈

typedef char STDataType;
//元素为char类型
typedef struct Stack
{STDataType* a;//动态的开辟空间int top;int capacity;
}ST;void StackInit(ST* ps)//初始化
{assert(ps);ps->a = (STDataType*)malloc(sizeof(STDataType) * 4);if (ps->a == NULL){printf("malloc fail\n");exit(-1);}ps->capacity = 4;ps->top = 0;//top一开始指向0位置（也可以指向-1位置）
}void StackDestory(ST* ps)//销毁
{assert(ps);free(ps->a);ps->a = NULL;ps->top = ps->capacity = 0;
}int StackSize(ST* ps)//元素个数
{assert(ps);return ps->top;//top从0开始
}void StackPush(ST* ps, STDataType x)//入栈
{assert(ps);//空间不够用 开辟空间if (ps->top == ps->capacity){STDataType* tmp = (STDataType*)realloc(ps->a, ps->capacity * 2 * sizeof(STDataType));if (tmp == NULL){printf("realloc fail\n");exit(-1);}else{ps->a = tmp;ps->capacity *= 2;}}ps->a[ps->top] = x;ps->top++;
}void StackPop(ST* ps)//出栈
{assert(ps);assert(ps->top > 0);ps->top--;
}STDataType StackTop(ST* ps)//取栈顶元素
{assert(ps);assert(ps->top > 0);return ps->a[ps->top - 1];
}bool StackEmpty(ST* ps)//判断是否为空
{assert(ps);return ps->top == 0;
}

题目求解

bool isValid(char * s){ST st;StackInit(&st);//字符串没有走到结束条件while((*s)!='\0'){if((*s) == '('||(*s) == '['||(*s) == '{'){StackPush(&st,*s);}else{if(StackEmpty(&st)){StackDestory(&st);//内存泄漏return false;}char top = StackTop(&st);StackPop(&st);if((*s == ')'&&top !='(')||(*s == ']'&&top !='[')||(*s == '}'&&top !='{')){StackDestory(&st);return false;}}s++;}bool ret = StackEmpty(&st);StackDestory(&st);return ret;
}