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[topcoder]HappyLetterDiv2

http://community.topcoder.com/stat?c=problem_statement&pm=13245

就是有字符串,里面的字符可以随意两两消除,如果不等的话,那么最后如果留下一个字符,这个字符就是winning letter。如果任意方法消除都是这个winning letter,叫做happy letter。求happy letter是否存在。题目其实就是找众数。要注意的是求完了还要扫一遍是不是大于length/2。

#include <string>using namespace std;class HappyLetterDiv2 {public:	char getHappyLetter(string letters)	{		char ch = letters[0];		int count = 1;		int n = letters.size();		for (int i = 1; i < n; i++)		{			if (count > 0 && letters[i] != ch)			{				count--;			}			else // count == 0 || letters[i] == ch			{				count++;				ch = letters[i];			}		}		count = 0;		for (int i = 0; i < n; i++)		{			if (letters[i] == ch)				count++;		}		if (count > n / 2)			return ch;		else			return ‘.‘;	}};