Please explain my mistake

#1

class Solution {
public:
bool isPalindrome(string s) {
//for (int i=0; i<s.length(); i++)
//tolower(s[i]);
int i=0,j= s.length()-1;
while(i<j){
if(!isalnum(s[i]))
i++;
else if(!isalnum(s[j]))
j–;
if(tolower(s[i])==tolower(s[j])){
i++;
j–;
}
else{
return false;
}
}
return true;
}
};

#2

@Prabhleen_sheenu consider a case when there are more than 1 consecutive non alphanumeric characters (eg:", ") here both comma and space needs to be ignored but you only ignored comma
So use while instead of if.

#3

Ohh.sir i added one more else loop is this fine too?

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image1036×790 27.7 KB

class Solution {
public:
bool isPalindrome(string s) {
//for (int i=0; i<s.length(); i++)
//tolower(s[i]);
int i=0,j= s.length()-1;
while(i<j){
if(!isalnum(s[i]))
i++;
else if(!isalnum(s[j]))
j–;
else{
if(tolower(s[i])==tolower(s[j])){
i++;
j–;
}
else{
return false;
}
}
}
return true;
}
};

#4

change these into while loops
while(!isalnum(s[i]))
i++;
while(!isalnum(s[j]))
j–;

#5

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