第一章 C++ 我来了——1.3 关于注释 & 1.4 While, For and If

1.3 注释

#include <iostream>
/* I am block comments
* The soft engineers like to employ the "*" as the head of the line to indicate
* this line is still a part of the block comments
*/

int main()
{
//I am single line comments, I can only protect the content in this line
return 0;
}

1.4 While, For and If

1.4.1 While

while (condition) while_body-statement;

#include <iostream>

int main ()
{
int sum = 0, val = 1;

while (val <= 10)
{
sum += val;
++val;
}

std::cout << "Sum of 1 to 10 inclusive is " << sum << std::endl;
return 0;
}

condition

condition

while_body_statement

0

condition

TRUE

1.4.2 For

#include <iostream>

int main ()
{
int sum = 0;

for (int val = 0; val <= 10; ++val)
sum += val;

std::cout << "Sum of 1 to 10 inclusive is " << sum << std::endl;
return 0;
}

1.4.3 If

#include <iostream>
//Calculate the sum of the numbers between v1 and v2
int main ()
{
std::cout << "Enter two numbers: " <<std::endl;
int v1, v2;
std::cin >> v1 >> v2;

int lower, upper;
if(v1 <= v2){
lower = v1;
upper = v2;
}
else{
lower = v2;
upper = v1;
}

int sum = 0;
for (int i = lower; i <= upper; ++i){
sum += i;
}
std::cout << sum <<std::endl;

return 0;
}

1.4.4 读入未知数目的输入

#include <iostream>

int main ()
{
int cout = 0, value;

while(std::cin >> value){
if(value < 0){
++cout;
}
}
std::cout << cout <<std::endl;

return 0;
}

std::cin >> value

Windows

ctrl

z

Unix

control-d

code

code

cout

1.5

1.6

类