ad hoc means something that is not known in advance
ANswer for ><<>> should be 0
Why so ?? I can see that I have valid string of length 4 here
Read the problem statement carefully it has asked for length of longest valid ‘prefix’ , so the expression must start with ‘<’. Hope it helps!
1 Like
They have asked “Prefix”. Read question again. Even first ‘>’ gives answer 0 as there is no valid prefix. There is no need to check further.
https://www.codechef.com/viewsolution/24353005
is my code, please let me know where’s the mistake.
I tried various test cases and they display correct output. I used pair parentheses algorithm to solve it and have then multiplied the count object by 2 to get the output.
Can someone plz point out the mistake here… i do not understand y this is giving WA.
I am getting the wrong answer, plz explain to me why.
#include<bits/stdc++.h>
#define fast ios_base::sync_with_stdio(false); cin.tie(NULL);
using namespace std ;
int main(void){
stack<char> mystack;
int t;
int i=0,ans=0;
string ch;
int l;
cin>>t;
while(t--){
ans=0;
i=0;
cin>>ch;
l=ch.size();
while(l--){
// cout<<mystack.empty()<<endl;
if(ch[i]=='<'){
mystack.push(ch[i]);
//cout<<"pushing"<<endl;
}
else if(!mystack.empty() and ch[i]=='>'){
mystack.pop();
//cout<<"poping"<<endl;
ans+=2;
}
else if(mystack.empty() and ch[i]=='>'){
break;
}
i++;
}
if(mystack.empty()){
cout<<ans<<endl;
}
else{
cout<<'0'<<endl;
}
}
}
i am also trying to find same thing if you get ans plz tell me to
Can someone plz tell me why i am getting WA ! which test case i am missing ?
https://www.codechef.com/viewsolution/26554850
How my solution is wrong ?
> #include<iostream>
> #include<stack>
> #include<vector>
> using namespace std;
>
> int main()
> {
> int t;
> vector<int> ans;
> cin>>t;
> while(t--)
> {
> stack<char> expr;
> string str;
> cin>>str;
> int sum=0;
> for(int i=0;i<str.length();i++)
> {
> if(str[i]=='<')
> expr.push(str[i]);
> else if(!expr.empty())
> {
> expr.pop();
> sum+=2;
> }
> else
> break;
> }
> ans.push_back(sum);
> }
> for(auto i=ans.begin();i!=ans.end();i++)
> cout<<*i<<"\n";
> return 0;
> }
>The answer is correct. It should be 0, since there are no "lapin"s at the prefix.
1 Like
Can anyone tell what’s wrong with this code?
#include <iostream>
#include <vector>
#include <stack>
using namespace std;
#define ull unsigned long long int
int getK(vector<char> s) {
stack<char> st;
int k=0;
for(int i=0; i<s.size(); i++) {
if(s[i]=='<') {
st.push('<');
}
else { // '>'
if(!st.empty()) {
st.pop();
k++;
}
else {
break;
}
}
}
return k;
}
int main() {
int T;
cin >> T;
while(T--) {
string ss;
cin >> ss;
vector<char> s(ss.begin(),ss.end());
int K = getK(s);
if(K==getK(vector<char>(ss.begin()+1,ss.end()))) cout << 0 << endl;
else cout << K*2 << endl;
}
}can anyone plz say why this is giving WA ?? Any particular case
Consider the testcase:
1
<<>
3 Likes
Kindly check why this is giving WA.
My logic : If ‘<’ increase top pointer. If ‘>’ decrease top pointer and increase length by 2 (1 for < and 1 for >)
Initial top pointer value = -1. If ‘>’ and top pointer is -1 it means no matching ‘<’ encountered…so return the current length of valid string till now.
Solution : CodeChef: Practical coding for everyone
Your solution fails on the testcase in the post above yours 
Yours is the only solution that I understood properly. Thanks for sharing!
I tried solving this problem with implementing concept of stack but it is giving WA. Although in my PC’s IDE it worked well.
Please once check my solution(CodeChef: Practical coding for everyone) it’s small.