括号匹配问题

思路

1. 遇见左括号入栈，遇见一个右括号弹出栈顶元素
2. 右括号入栈前如果栈已经为空，则不匹配
3. 如果不为空则读取并弹出，弹出来的元素与右括号做比较，必须匹配，不匹配返回false;
4. 如果最后栈里还有元素，则说明不匹配

c版本实现

typedef struct Stack{int array[1000000];int top;
} Stack;//初始化
void StackInit(Stack *stack){stack->top = 0;
}
//压栈(顺序表的尾插)
void StackPush(Stack *stack, int value){stack->array[stack->top] = value;stack->top++;
}
//出栈,弹出
void StackPop(Stack *stack){stack->top--;
}
//返回栈顶元素
int StackTop(const Stack *stack){return stack->array[stack->top - 1];
}
//判断是否为空
int StackEmpty(const Stack *stack){return stack->top == 0 ? 1 : 0; 
}
//获取size
int StackSize(const Stack *stack){return stack->top;
}//1. 括号匹配
bool isValid(char * s){Stack stack;StackInit(&stack);while (*s != '\0'){switch (*s){case'{':case'[':case'(':StackPush(&stack, (int)*s); break;case'}':case']':case')':if (StackEmpty(&stack)){return false;}char left = (char)StackTop(&stack);StackPop(&stack);if (!(left == '('&&*s == ')'|| left == '['&&*s == ']'|| left == '{'&&*s == '}')){return false;}break;default:break;}s++;}if (!StackEmpty(&stack)){return false;}return true;
}

c++版本实现

#include<stack>
#include<string>
class Solution {
public:bool isValid(string s) {stack<char> st1;for(int i=0;i<s.size();i++){char ch =s[i];switch(ch){case'{':case'[':case'(':st1.push(ch);break;case'}':case']':case')':if(st1.empty()){return false;}char left =st1.top();st1.pop();if(!(left == '('&&ch == ')'|| left == '['&&ch == ']'|| left == '{'&&ch == '}')){return false;}break;}}      if(!st1.empty()){return false;}else{return true;}}};