力扣-最长回文字符串（马拉车算法）

力扣-最长回文字符串（马拉车算法）

#include 
#include 
#include 
using namespace std;
string longestPailndrome(string newSource)
{
	int left = 0, right = newSource.length();//记录字符串的最左最右边界
	int center = 0, half_size = 0;//记录最长回文字符串的中心以及半径
	int max_right = 0;//记录当前访问位置回文子串右半径最大覆盖范围
	int *cover = new int[right];//记录字符串每个位置回文子串的覆盖半径
	for (int i = 0; i < newSource.length(); i++)
	{
		if (i < max_right) //i在max_right的左边
		{
			cover[i] = min(cover[2 * center - i], max_right - i);
		}
		else  //i在max_right的右边
		{
			cover[i] = 1;
		}
		while (i - cover[i] >=left && i + cover[i] < right&&newSource[i - cover[i]] == newSource[i + cover[i]])
		{
			cover[i] += 1;
		}
		//更新max_right
		if (cover[i] + i - 1 > max_right)
		{
			max_right = cover[i];
		}
		//更新center,half_size
		if (cover[i] >= half_size)
		{
			half_size = cover[i];
			center = i;
		}
	}
	delete[]cover;
	string tempString = newSource.substr(center - half_size + 1, 2 * half_size - 1);
	//从tempString中删去字符'#'
	tempString.erase(remove(tempString.begin(), tempString.end(), '#'), tempString.end());
	return tempString;
}
string changeString(const string &source)
{
	int len = 2*source.length()+1;
	char *root = new char[len];
	root[0] = '#';
	unsigned j = 1;
	for (unsigned i = 0; i < source.length(); i++)
	{
		root[j++] = source[i];
		root[j++] = '#';	
	}
	string newSource = root;
	delete[]root;
	return newSource.substr(0,len);
}
int main()
{
	string source;
	string newSource;
	string maxString;
	cout << "input a string: ";
	cin >> source;
	newSource = changeString(source);
	maxString = longestPailndrome(newSource);
	cout << "source string is: " << source << endl;
	cout << "new source string is: " << newSource << endl;
	cout << "the longest pailndrome is: " << maxString << endl;
	return 0;
}