C++primer习题6.2节练习

练习6.10

#include "stdafx.h"
#include "iostream"
#include "stddef.h"
#include<vector>
using namespace std;
//2018_7_26 
void exchange(int *p, int *q);
int main()
{
	cout << "please enter two numbers" << endl;
	int x1, x2;
	cin >> x1 >> x2;
	exchange(&x1,&x2);
	cout <<"x1："<< x1<<"  x2:" << x2 << endl;
	system("pause");
	return 0;
}

void exchange(int *p, int *q)
{
	int temp;
	temp = *p;
	*p = *q;
	*q = temp;
}

6.11

#include "stdafx.h"
#include "iostream"
#include "stddef.h"
#include<vector>
using namespace std;
//2018_7_26 
void reset(int &x);
int main()
{
	int x;
	cin >> x;
	reset(x);
	cout << x << endl;
	system("pause");
	return 0;
}

void reset(int &x)
{
	x = 9999;
}

6.12

#include "stdafx.h"
#include "iostream"
#include "stddef.h"
#include<vector>
using namespace std;
//2018_7_26 
void exchange(int &p, int &q);
int main()
{
	cout << "please enter two numbers" << endl;
	int x1, x2;
	cin >> x1 >> x2;
	exchange(x1, x2);
	cout << "x1：" << x1 << "  x2:" << x2 << endl;
	system("pause");
	return 0;
}

void exchange(int &p, int &q)
{
	int temp;
	temp = p;
	p = q;
	q = temp;
}

6.13

完整的寻找特定字符的程序

#include "stdafx.h"
#include "iostream"
#include "stddef.h"
#include "string"
#include<vector>
using namespace std;
//2018_7_26 

int find(const string &s, char theone, int &count);
int main()
{
	string s;
	cout << "输入字符串" << endl;
	cin >> s;
	char theone;
	cout << "输入要找的字母" << endl;
	cin >> theone;
	int count;
	cout << "第一次出现的位置为:" << find(s, theone, count)+1<< endl;
	cout << "出现次数为:" << count << endl;
	system("pause");
	return 0;
}

int find(const string &s, char theone, int &count)
{
	auto ret = s.size();
	count = 0;
	for (decltype(ret) i = 0;i != s.size();++i)
	{
		if (s[i] == theone)
		{
			if (ret == s.size())
				ret = i;
			++count;
		}
	}
	return ret;
}

6.17

#include "stdafx.h"
#include "iostream"
#include "stddef.h"
#include "string"
#include<vector>
using namespace std;
//2018_7_28 判断是否有大写字母 
void judge(const string &s);
int main() {
	cout << "请输入要检查的字符串" << endl;
	string s;
	cin >> s;
	judge(s);
	system("pause");
	return 0;
}

void judge(const string &s)
{
	int flag = 0;
	for (auto c : s)//用这个for循环对字符串内的每个对象进行操作
	{
		if (!islower(c))
		{
			cout << "这个字符串有大写字母" << endl;
			flag = 1;
			break;
		}
	}
	if (flag ==0)
		cout << "这个字符串没大写字母" << endl;
}

6.21

#include "stdafx.h"
#include "iostream"
#include "stddef.h"
#include "string"
#include<vector>
using namespace std;
//2018_7_26 

int exchange(int x1, int *p1);
int main() {
	cout << "请输入两个数" << endl;
	int x1, x2;
	int *p1;
	cin >> x1 >> x2;
	p1 = &x2;//第二个数将由指针所指
	cout << "较大值为" << exchange(x1, p1) << endl;;
	return 0;
}

int exchange(int x1, int *p1)
{
	if (x1 >= *p1)
		return x1;
	else return *p1;
}