Topcoder712B

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]<<"
";
		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<<"
";
			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]<<"
";
		if(mp[i]&1) {
			for(int j=0;j<mp[i];j++) {
				f.push_back(i);
			}
			ret.push_back(f);
		}
	}
	return ret;
 }

}