1.确定一个字符串每个字符都是独一无二的

//Implement an algorithm to determine if a string has all unique characters What if
//you can not use additional data structures?
#include <iostream>
#include <string>
using namespace std;
//适合所有ascii字符

bool uniquechar1(string & s)
{
bool a[256]={0};//ascii为256个
int temp;
for (auto i =0;i<s.size();i++)
{
temp=s[i];
if(a[temp]) return false;
a[temp] =true;
}
return true;
}
//只适合全为字母的字符串
bool uniquechar2(string & s)
{
int temp;
int val =0;
for (auto i =0;i<s.size();i++)
{
temp=s[i]-'a';
if((val&(1<<temp))>0) return false;
val |=(1<<temp);
}
return true;
}

void main()
{
string b;
std::cin>>b;
std::cout<<uniquechar1(b)<<" "<<uniquechar2(b);
system("pause");
}