C＃：运算符'！='不能应用于类型'object'和'char'的操作数

Question

I am a new learner and trying to solve a problem on the Leetcode, but there was a compile error.

public class Solution 
{
public bool IsValid(string s) 
{
    if(s.Length%2==1)
    {
        return false;
    }
    if(s.Length==0)
    {
        return true;
    }
    Stack st=new Stack();
    for(int i=0;i<s.Length;i++)
    {
        switch(s[i])
        {
            case '(':
            st.Push(s[i]);
            break;
            case'[':
            st.Push(s[i]);
            break;
            case'{':
            st.Push(s[i]);
            break;
            case ')':
            if(st.Count==0||st.Peek()!='(')
            {
                return false;
            }
            else
            {
                st.Pop();
            }
            break;
            case']':
            if(st.Count==0||st.Peek()!='[')
            {
                return false;
            }
            else
            {
                st.Pop();
            }
            break;
            case'}':
            if(st.Count==0||st.Peek()!='}')
            {
                return false;
            }
            else
            {
                st.Pop();
            }
            break;
        }
    }
    return st.Count==0;
}
}

I get an error.

Line 28: Operator '!=' cannot be applied to operands of type 'object' and 'char'

Might be this one

if(st.Count==0||st.Peek()!='(')    

I know this is about datatype, but I don't know how to solve it.

I am not an English speaker so some of my English grammar might be crazy. Sorry about that, and thank you if you can help me.

Answer 1

Stack stores objects, but you want to store char specifically. Use Stack<char> instead.

  Stack<char> st = new Stack<char>();

Answer 2

You are getting the error because you are using a Stack without generics. Your stack is a stack of type Object .

You would need to cast the data you pop or peek from your stack to char .

example:

if(st.Count==0|| (char) st.Peek()!='(')