Topcoder712B

Posted 2020-10-27 passion27

Problem Statement
	You have some cards. Each card contains a single lowercase letter. You are given these letters as the characters of the string card. A palindrome is a string that reads the same forwards and backwards. Examples of palindromes: "eve", "abba", "aaaaaa", and "racecar". Use the cards you have to spell some palindromes. In particular: Each card must be used in exactly one of the palindromes. The total number of palindromes must be as small as possible. Return a vector <string> containing the palindromes you built. (Each element of the return value should be one of the palindromes.) A solution always exists. If there are multiple optimal solutions, you may choose and output any one of them.
Definition
	Class: MakePalindrome Method: constructMinimal Parameters: string Returns: vector <string> Method signature: vector <string> constructMinimal(string card) (be sure your method is public)
Limits
	Time limit (s): 2.000 Memory limit (MB): 256 Stack limit (MB): 256
Constraints
-	card will contain between 1 and 1,000 characters, inclusive.
-	Each character in card will be a lowercase English letter (‘a‘-‘z‘).
Examples
0)
	"abbaa" Returns: {"ababa" } We can rearrange all letters into a single palindrome. There are two ways to do so: one is "ababa", the other is "baaab".
1)
	"abc" Returns: {"a", "b", "c" } This time the only solution is to build three palindromes, each consisting of a single letter. Note that you may return the three strings in any order.
2)
	"aaabbbccc" Returns: {"aba", "bcb", "cac" } There are other solutions like {"aaa", "bbb", "ccc"}
3)
	"topcoder" Returns: {"oco", "d", "e", "p", "r", "t" }
4)
	"z" Returns: {"z" }

public class MakePalindrome
{
vector  constructMinimal(string card) {
	map<char, int> mp;
	mp.clear();
	vector ret;
	ret.clear();
	for(int i=0;i<card.size();i++) {
		mp[card[i]] ++;
	}
	string f = "";
	for(char i = ‘a‘; i <= ‘z‘; i++) {
		// cout<<i<<" "<<mp[i]<<"\n";
		if(mp[i] % 2 == 0) {
			for(int j=0;j<mp[i]/2;j++) {
				f.push_back(i);
			}
			mp[i] = 0;
		}
	}
	bool flag = 0;
	// Add character with odd occurrence
	for(char i = ‘a‘; i <= ‘z‘; i++) {
		if(mp[i]&1) {
			flag = 1;
			for(int j=0;j<mp[i]/2;j++) {
				f.push_back(i);
			}
			string temp = f;
			cout<<temp<<"\n";
			reverse(temp.begin(), temp.end());
			f = f + i + temp;
			mp[i] = 0;
			break;
		}
	}
	// if all characters are of even occurrence
	if(!flag){
		string temp = f;
		reverse(temp.begin(), temp.end());
		f = f + temp;
		ret.push_back(f);
		return ret;
	}

	ret.push_back(f);
	f = "";
	// for all other characters of odd occurrence
	for(char i = ‘a‘; i <= ‘z‘; i++) {
		f = "";
		// cout<<i<<" "<<mp[i]<<"\n";
		if(mp[i]&1) {
			for(int j=0;j<mp[i];j++) {
				f.push_back(i);
			}
			ret.push_back(f);
		}
	}
	return ret;
 }

}