数据结构 栈和队列的应用
在昨天分享了有关栈和队列的基础知识和基本操作后，今天来分享一些有关栈和队列的应用
栈和队列的应用
- 删除字符串中的所有相邻重复项
#include
#include
using namespace std;
string remove(string S)
{
stack charStack;
for (int i = 0; i < S.length(); ++i)
{
char c=S[i];
if (!charStack.empty() && charStack.top() == c)
{
charStack.pop();
}
else
{
charStack.push(c);
}
}
string result;
while (!charStack.empty())
{
result = charStack.top() + result;
charStack.pop();
}
return result;
}
int main()
{
string in;
cin >> in;
string result = remove(in);
cout< - 括号匹配问题(类比20.LeetCode 有效的括号）
#include
#include
#include
using namespace std;
bool match(string input)
{
stack s;
for (int i = 0; i < input.length(); i++)
{
char bracket = input[i];
if (bracket == '(' || bracket == '{' || bracket == '[')
{
s.push(bracket);
}
else if (bracket == ')' || bracket == '}' || bracket == ']')
{
if (s.empty())
{
return false;
}
char top = s.top();
s.pop();
if ((bracket == ')' && top != '(') || (bracket == '}' && top != '{') || (bracket == ']' && top != '['))
{
return false;
}
}
}
return s.empty();
}
int main()
{
string input;
cin >> input;
if (match(input))
{
cout << "yes" << endl;
}
else
{
cout << "no" << endl;
}
return 0;
}
- 计算后缀表达式
#include
#include
#include
#include
#include
using namespace std;
int customAtoi(const string &str)
{
int result = 0;
int sign = 1;
size_t i = 0;
if (str[0] == '-')
{
sign = -1;
i = 1;
}
for (; i < str.length(); i++)
{
if (isdigit(str[i]))
{
result = result * 10 + (str[i] - '0');
}
else
{
cerr << "Error: Invalid character in input: " << str[i] << endl;
std::exit(1);
}
}
return result * sign;
}
bool isOperator(const string &token)
{
return (token == "+" || token == "-" || token == "*");
}
int evaluatePostfixExpression()
{
stack operands;
string token;
while (cin >> token)
{
if (token == "#")
{
break;
}
if (!isOperator(token))
{
operands.push(customAtoi(token));
}
else
{
int operand2 = operands.top();
operands.pop();
int operand1 = operands.top();
operands.pop();
int result;
if (token == "+")
{
result = operand1 + operand2;
}
else if (token == "-")
{
result = operand1 - operand2;
}
else if (token == "*")
{
result = operand1 * operand2;
}
operands.push(result);
}
}
if (!operands.empty())
{
return operands.top();
}
cerr << "Error: Invalid expression." << endl;
std::exit(1);
}
int main()
{
int result = evaluatePostfixExpression();
cout << result << endl;
return 0;
}
- 表达式求值
#include
#include
#include
#include
using namespace std;
int precedence(char op)
{
if (op == '+' || op == '-')
{
return 1;
}
else if (op == '*' || op == '/')
{
return 2;
}
return 0;
}
int evaluateExpression(const string &expression)
{
stack values;
stack operators;
for (size_t i = 0; i < expression.length(); i++)
{
if (isspace(expression[i]))
{
continue;
}
else if (isdigit(expression[i]))
{
int num = 0;
while (i < expression.length() && isdigit(expression[i]))
{
num = num * 10 + (expression[i] - '0');
i++;
}
i--;
values.push(num);
}
else if (expression[i] == '(')
{
operators.push(expression[i]);
}
else if (expression[i] == ')')
{
while (!operators.empty() && operators.top() != '(')
{
char op = operators.top();
operators.pop();
int operand2 = values.top();
values.pop();
int operand1 = values.top();
values.pop();
if (op == '+')
{
values.push(operand1 + operand2);
}
else if (op == '-')
{
values.push(operand1 - operand2);
}
else if (op == '*')
{
values.push(operand1 * operand2);
}
else if (op == '/')
{
values.push(operand1 / operand2);
}
}
operators.pop();
}
else if (expression[i] == '+' || expression[i] == '-' || expression[i] == '*' || expression[i] == '/')
{
while (!operators.empty() && operators.top() != '(' && precedence(operators.top()) >= precedence(expression[i]))
{
char op = operators.top();
operators.pop();
int operand2 = values.top();
values.pop();
int operand1 = values.top();
values.pop();
if (op == '+')
{
values.push(operand1 + operand2);
}
else if (op == '-')
{
values.push(operand1 - operand2);
}
else if (op == '*')
{
values.push(operand1 * operand2);
}
else if (op == '/')
{
values.push(operand1 / operand2);
}
}
operators.push(expression[i]);
}
}
while (!operators.empty())
{
char op = operators.top();
operators.pop();
int operand2 = values.top();
values.pop();
int operand1 = values.top();
values.pop();
if (op == '+')
{
values.push(operand1 + operand2);
}
else if (op == '-')
{
values.push(operand1 - operand2);
}
else if (op == '*')
{
values.push(operand1 * operand2);
}
else if (op == '/')
{
values.push(operand1 / operand2);
}
}
return values.top();
}
int main()
{
string expression;
getline(cin, expression);
int result = evaluateExpression(expression);
cout << result << endl;
return 0;
}
- 回文链表
#include
using namespace std;
struct Node
{
int data;
Node *next;
};
void createList(Node *&h,int n)
{
Node *p,*r;
h=new Node;
h->next=NULL;
r=h;
for(int i=1; i<=n; i++)
{
p=new Node;
cin>>p->data;
r->next=p;
r=p;
}
r->next=NULL;
}
void printList(Node *h)
{
Node *p;
p=h->next;
while(p)
{
cout<data<<" ";
p=p->next;
}
cout<next)
{
return true;
}
Node *slow = head;
Node *fast = head;
while (fast && fast->next)
{
slow = slow->next;
fast = fast->next->next;
}
Node *prev = NULL;
Node *curr = slow;
while (curr)
{
Node *next = curr->next;
curr->next = prev;
prev = curr;
curr = next;
}
Node *left = head->next;
Node *right = prev;
while (left && right)
{
if (left->data != right->data)
{
return false;
}
left = left->next;
right = right->next;
}
return true;
}
int main()
{
int n;
Node *h;
cin>>n;
createList(h,n);
cout<<(isPalindrome(h)?"yes":"no");
return 0;
}