ex6.18, 6.20, 6.21

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Exercise 6.18

输入两个string对象，比较哪个按字典序靠前。

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#include <iostream>
#include <string>

using std::cin;
using std::cout;
using std::endl;
using std::string;

string dictOrder(string a, string b) 
{
	const char *cp1 = a.c_str();
	const char *cp2 = b.c_str();
	while (*cp1 && *cp2)
	{
		if (*cp1 != *cp2)
		{
			return *cp1 > *cp2 ? "First bigger" : "First smaller";
		}
		cp1++;
		cp2++;
	}
	return "Same";
}

int main()
{
	string str1, str2;
	cout << "Please input two strings.\nIf you want to quit, input two 'q'." << endl;
	do {
		cout << "\nTwo strings:\n";
		cin >> str1 >> str2;
		cout<< dictOrder(str1, str2) << endl;
	} while (str1 != "q" && str2 != "q");

	return 0;
}

outputs

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Please input two strings.
If you want to quit, input two 'q'.

Two strings:
ab↙
ac↙
First smaller

Two strings:
b↙
a↙
First bigger

Two strings:
q↙
q↙
Same

Exercise 6.20

读入一系列string，直到出现重复的单词时停止，或者没有重复时请说明。

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#include <iostream>
#include <vector>

using std::cin;
using std::cout;
using std::endl;
using std::vector;

int main()
{
	vector<string> v;
	string str;
	bool found = false;
	while ( !found && cin >> str)
	{
		for (size_t i = 0; i < v.size(); i++)
		{
			if (str == v[i]) 
			{
				found = true;
				break;
			}
		}
		v.push_back(str);
	}
	cout << (found ? "Repeat found" : "No repeated") << endl;
	
	return 0;
}

outputs

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// test1
hi↙
hey↙
hello↙
hi↙
Repeat found

// test2
hi↙
hey↙
hello↙
^Z↙
No repeated

Exercise 6.21

读入一系列string，直到出现重复的以大写字母开头的单词时停止，或者没有重复时请说明。

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#include <iostream>
#include <vector>

using std::cin;
using std::cout;
using std::endl;
using std::vector;

bool isUpper(char ch) {
	return (ch >= 'A' && ch <= 'Z');
}

int main()
{
	vector<string> v;
	string str;
	bool found = false;
	while ( !found && cin >> str)
	{
		for (size_t i = 0; i < v.size(); i++)
		{
			if (str == v[i]) 
			{
				found = true;
				break;
			}
		}
		if (isUpper(str[0]))
		{
			v.push_back(str);
		}
	}
	cout << (found ? "Repeat found" : "No repeated") << endl;
	
	return 0;
}

outputs

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// test1
hi↙
hI↙
Hi↙
HI↙
Hi↙
Repeat found

// test2
hi↙
hI↙
Hi↙
HI↙
^Z↙
No repeated