Stack Introduction

Related videos:

Data Structures Source Code:

[anj]

Coding the parentheses check problem on leetcode was so easier after watching this video. Just some syntax error but an efficient solution. Thank you William!

[kasperbaun]

Thanks a bunch for creating all these awsome videos on data structures!

[vovanhung]

I'm so proud of when my country has one problem which all dev can know is Hanoi tower. 🙌🙌🙌🙌❤❤❤❤

[nomd]

Shouldn’t stacks be o(n) in size since it holds n items

[vinayshivakumar]

Good explanation. But, I think pseudo-code for valid parenthesis problem is incomplete or incorrect or I have not understood correctly. Can you please provide the actual code? Below is what I implemented and with your pseudo code if we have input as "()", then it will try to getReversedBracket(")") i.e for ")" this also, so I am confused with that.
public boolean isValid(String s) {
Stack stack = new Stack();
for( int i=0; i < s.length(); i++ ){
String c =
if( c.equals("{") || c.equals("(") || c.equals("[") ){
stack.push(c);
}
else{
if( !stack.isEmpty()){
String rev =
if( c.equals(rev) )
stack.pop();
else
return false;
}
else
return false;
}
}
if( stack.isEmpty())
return true;
else
return false;
}

public String getReverseBracker(String s){
if(s.equals("{"))
return "}";
else if(s.equals("("))
return ")";
else if(s.equals("["))
return "]";
return "";
}