5.1
空语句就是一个单独的分号；在程序的某个地方语法上需要一条语句但是逻辑上不需要，此时应该使用空语句
5.2
用花括号括起来的语句序列，在程序的某个地方语法上需要一条语句，但逻辑上需要多条语句时用
5.3
//p5_3.cpp
#include <iostream>
int main()
{
int sum = 0;
for (int val = 1; val <= 10; sum += val, ++val )
{
;
}
std::cout << "Sum of 1 to 10 inclusive is " << sum << std::endl;
return 0;
}
5.4
a ) iter 没有初始化
string::iterator iter = s.begin();
while(iter != s.end())
{}
b ) 不需要if 语句
5.5
//p5_5.cpp --
#include <iostream>
#include <string>
#include <vector>
using namespace std;
int main()
{
const vector<string> scores = {"F", "D", "C", "B", "A", "A++"};
string lettergrade;
int grade;
cin >> grade;
if(grade<60)
lettergrade = scores[0];
else
{
lettergrade = scores[(grade - 50)/10];
if (grade != 100)
{
if(grade%10 > 7)
lettergrade += "+";
else if(grade%10 < 3)
lettergrade += "-";
}
}
cout << grade <<" : " << lettergrade << endl;
return 0;
}
5.6
//p5_6.cpp -- 改写5.5
#include <iostream>
#include <string>
#include <vector>
using namespace std;
int main()
{
const vector<string> scores = {"F", "D", "C", "B", "A", "A++"};
string lettergrade;
int grade;
cin >> grade;
grade<60 ? lettergrade = scores[0]:
lettergrade = scores[(grade - 50)/10],((grade != 100) && (grade%10 > 7))? lettergrade += "+" :
(grade%10 < 3)? lettergrade += "-": lettergrade ;
cout << grade <<" : " << lettergrade << endl;
return 0;
}
5.7
a )
if(ival1 != ival2)
ival1 = ival2; //加分号
else
ival1 = ival2 = 0;
b )
if (ival1 < minval)
{
minval = ival;
occurs = 1;
}
c )
if (int ival = get_value())
cout << "ival = " << ival << endl;
else
cout << "ival = 0\n";
d )
if (ival == 0)
ival = get_value();
一些题比较简单就不浪费时间了
5.9
//p5_9.cpp -- 使用if统计元音字母
#include <iostream>
using namespace std;
int main()
{
char temp;
int count = 0;
while(cin >> temp)
if(temp == 'a'||temp == 'e'||temp =='i'||temp == 'o'|| temp == 'u')
++count;
cout << "count = " << count << endl;
return 0;
}
5.12
//p5_12.cpp
#include <iostream>
using namespace std;
int main()
{
char temp;
unsigned ffCnt = 0, flCnt = 0, fiCnt = 0;
while(cin >> temp)
{
if(temp == 'f')
{
if(cin >> temp)
{
switch(temp)
{
case 'f': ffCnt++;
break;
case 'l': flCnt++;
break;
case 'i': fiCnt++;
break;
default: break;
}
}
}
}
cout << "ffCnt = " << ffCnt << endl;
cout << "flCnt = " << flCnt << endl;
cout << "fiCnt = " << fiCnt << endl;
return 0;
}
5.14
//p5_14.cpp
#include <iostream>
#include <vector>
#include <string>
using namespace std;
int main()
{
string temp;
string strTemp = "\0"; //临时存储正在统计的单词
string strMax; //存储当前连续出现次数最多的单词
unsigned strCnt = 0, strTempCnt = 0; //strCnt当前连续出现最多次数，strTempCnt当前统计单词连续出现次数
while(cin >> temp)
{
if(strTemp == "\0" )
{
strTemp = temp;
++strTempCnt;
}
else if(strTemp == temp)
{
++strTempCnt;
}
else
{
if(strTempCnt >= strCnt )
{
strMax = strTemp;
strCnt = strTempCnt;
}
strTemp = temp;
strTempCnt = 1;
}
}
if(strCnt < 2)
cout << "have no word continuously appear!" << endl;
else
{
cout << strMax << " "<< strCnt << " times " << endl;
}
return 0;
}
5.17
//p5_17.cpp
#include <iostream>
#include <vector>
#include <iostream>
#include <vector>
using namespace std;
int main()
{
vector<int> ivec1 = { 0, 1, 2 };
vector<int> ivec2 = { 0, 1, 1, 2, 3, 5, 8 };
//int temp;
//while(cin >> temp) //想通过交互式的读取数据，但是每次只有第一个while循环能够成功读取，第二个while循环就只接跳过了
// ivec1.push_back(temp); //有什么解决方案，请不吝赐教
{
vector<int> ivec1 = { 0, 1, 2 };
vector<int> ivec2 = { 0, 1, 1, 2, 3, 5, 8 };
//int temp;
//while(cin >> temp) //想通过交互式的读取数据，但是每次只有第一个while循环能够成功读取，第二个while循环就只接跳过了
// ivec1.push_back(temp); //有什么解决方案，请不吝赐教
//while(cin >> temp)
// ivec2.push_back(temp);
// ivec2.push_back(temp);
auto n = (ivec1.size() < ivec2.size()) ? ivec1.size() : ivec2.size();
decltype(ivec1.size()) i = 0;
for (; i < n; ++i)
{
if (ivec1[i] != ivec2[i])
break;
}
decltype(ivec1.size()) i = 0;
for (; i < n; ++i)
{
if (ivec1[i] != ivec2[i])
break;
}
bool isPrefix = (i == n) ? true : false;
if (isPrefix)
cout << "true" << endl;
else
{
cout << "false" << endl;
}
cout << "true" << endl;
else
{
cout << "false" << endl;
}
return 0;
}