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HackerEarth- Candies.cpp
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HackerEarth- Candies.cpp
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#include<bits/stdc++.h>
using namespace std;
string s;
int n;
bool pali(int len)
{
int hashing[130];
memset(hashing,0,sizeof(hashing));
int v,fr=0;
for(int i=0;i<s.size();i++)
{
v=(int)(s[i]);
if(i<len)
{
hashing[v]++;
if(hashing[v]%2==0) fr++;
}
else{
hashing[v]++;
if(hashing[v]%2==0) fr++;
int left=(int)s[i-len]; // right side (i) is incrementing ,so left side should be subtracted to keep n size subtring all data fixed
hashing[left]--;
if(hashing[left]%2==1) fr--;// window sliding technique ,alltime keep data of length of substring n
}
if(fr>=(n/2))
return 1;
}
if(fr>=n/2) // if fr (2 times) occurs equal or more than half of the required size substring , then it can be rearranged to a palindrome of size n
return 1;
return 0;
}
int main()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
cout.tie(0);
cin>>s;
int q;
cin>>q;
while(q--)
{
cin>>n;
int low=n,high=(int)s.size(),mid,ans=-1;
while(low<=high) // if n length palindrome can't be taken from n length substring ,then we have to choose minimum length substring from where we can choose n length palindrome
{
mid=(low+high)/2;
if(pali(mid)) ans=mid,high=mid-1;
else low=mid+1;
}
cout<<ans<<'\n';
}
return 0;
}