update palindrome.cpp

I improved the existing code so that it can now handle sentences with punctuation and spaces. This means that it now works for an edge case like "Sit on a potato pan, Otis"

algorithms/CPlusPlus/Maths/palindrome.cpp

@@ -1,6 +1,7 @@
 // Program to find whether a number and word is palindrome or not.
 
 #include<iostream>				//header file
+#include<ctype.h>
 using namespace std;
 int main()						//Main function
 {
@@ -8,14 +9,34 @@ int main()						//Main function
 	cin >> num_str;			//taking input from user
 	string new_str = "";		//define a new variable
 
-	for(int x = (num_str.size()-1); x >= 0; x--){		//for loop started
+	
-		new_str += num_str[x];							//assigning the value input by user to new variable in reverse order
+	string test_str = "";		//define new variables for cleaning the input
+	string low = "";
+	char temp;
+	int i;
+
+	for(i = 0; i < num_str.size(); i++){				//make num_str all lower case and remove all punctuation and spaces
+		temp = num_str[i];
+		if(isalnum(temp)){
+			low = char(tolower(temp));			//converting the character to be lower case
+			test_str.append(low);				//adding that lowercase character to the new string
+		}
+	}
+	for(int x = (test_str.size()-1); x >= 0; x--){		//for loop started
+		new_str += test_str[x];							//assigning the value input by user to new variable in reverse order
 	}													//for loop end
 	
-	cout << (num_str == new_str ? "palindrome" : "Non-palindrome");			//checking whether the value assigned to both variables is equal or not using ternary operator and printing whether it's palindrome or non-palindrome
+	string pal = "";
+	if(test_str == new_str){	//checking if the variables are equal and setting a string according to the result
+		pal = "palindrome";
+	}else{
+		pal = "Non-palindrome";
+	}
+	cout << pal;			//printing if it is a palindrome or non-palindrome
 
 	return 0;					//returning the main function
 }
 
 //complexity of the program is O(n)
 //test cases:- 101,pop,asdfgfdsa,123454321,obobo,nancyiycnan etc.
+//additional test cases: "Sit o,n a 'potat+o pan, Otis", "Sit on a potato pan, Otis"