Create strlower() function to convert std::string to lowercase.

util.h

@@ -0,0 +1,16 @@
+
+#ifndef _UTIL_H_
+#define _UTIL_H_
+
+#include<cstring>
+
+inline std::string strlower(const std::string &s)
+{
+	int l = s.length();
+	std::string sl = s;
+	for (int i = 0; i < l; i++)
+		sl[i] = tolower(sl[i]);
+	return sl;
+}
+
+#endif // _UTIL_H_