Read the How to prepare for an interview series at my blog: http://se7so.blogspot.com/2014/01/how-to-prepare-for-interview.html

prob1.cpp

bool hasUniqueChs(string s) {
	bool chs[256];
	
	memset(chs, false, sizeof chs);
	
	for(int i = 0; i < s.size(); i++) {
		if(chs[s[i]])
			return false;
		chs[s[i]] = true;
	}
	
	return true;
}