请写出代码。旋转字符串："waterbottle"是"erbottlewat"的旋转字符串。

简答题：

#include <iostream>
#include <string>

bool isSubstring(const std::string& vSource, const std::string& vSubStr)
{
	if (vSource.find(vSubStr) != std::string::npos) return true;
	return false;
}

bool isRotate(const std::string& vLeft, const std::string& vRight)
{
	if (vLeft.length() != vRight.length()) return false;
	return (vLeft+vLeft, vRight);
}

int main()
{
	std::cout << isRotate("dayup", "upday") << std::endl;
	return 0;
}