1
int a = 1;
2
double b = .1e2;
3
char c = 'A';

1
#include <iostream>
2
using namespace std;
3
int main(){
4
  char a[10];
5
  cin >> a ; // 假设输入 "Hello"
6
  cout << a << " world" << endl; //输出 "Hello world"
7
  return 0;
8
}

1
double amount = 12618.98;
2
double interestRate = 0.0013;
3
double interest = amount * interestRate;
4

5
cout << "Interest is:"<<interest<<endl;
6
Interest is: 16.4047
7

8
cout << "Interest is:" <<fixed<<setprecision(2)<<interest<<endl;
9
Interest is: 16.40

1
double d = 3; // int被自动提升为float；仅适用于低等级转换为高等级

1
int i = static_cast<int>(3.0); // (type narrowing) (类型缩窄)
2
int i = (int)3.9; // (Fraction part is truncated) (小数点后被丢弃)

1
double d = 4.5;
2
int i = static_cast<int>(d);  // d is not changed

1
char ch = 'A';
2
cout << ch << " " << int(ch) << endl;
3
ch++;
4
cout << ch << " " << int(ch) << endl;

1
int i = 'a'; // Same as int i = (int)'a';
2
char c = 97; // Same as char c = (char)97;

1
char c = 0xFF41;
2
cout<<c<<endl;

1
char c = 65.25;
2
cout<<c<<endl;

1
int i = ‘A’;
2
cout<<i;

1
cout<<“He said \"programming is fun!\""<<endl;
2
cout<<"\\t is a tab character"<<endl;
3
cout << "A\tB\tC\n1\t2\t3\n";

1
bool lightOn = true;

1
#include <iostream>
2
int main() {
3
    int a = 5;
4
    int b = 3;
5
    int c = 2;
6
    int d = a + b * c -!a && c++ % a;
7
    std::cout << "d = " << d << std::endl;
8
    std::cout << "c after evaluation = " << c << std::endl;
9
    return 0;
10

11
}

1
if (booleanExpression) {
2
  statement(s)-for-the-true-case;
3
}
4
else {
5
  statement(s)-for-the-false-case;
6
}

1
switch (status) {
2
  case 0:  compute taxes for single filers;
3
           break;
4
  case 1:  compute taxes for married file jointly;
5
           break;
6
  case 2:  compute taxes for married file separately;
7
           break;
8
  case 3:  compute taxes for head of household;
9
           break;
10
  default: cout << “Error: invalid statud!”;
11
}

1
while (loop-continuation-condition){
2
  // loop-body;
3
  Statement(s);
4
}

1
int count = 0;
2
while (count < 1000){
3
  cout << "Hello World!\n";
4
  count++;
5
}

1
do
2
{
3
  // Loop body;
4
  Statement(s);
5
} while (loop-continuation-condition);

1
for (initial-action; loop-continuation-condition; action-after-each-iteration){
2
   // loop body;
3
   Statement(s);
4
}

1
int i;
2
for (i = 0; i < 100; i++){
3
  cout << "Welcome to C++!\n";
4
}

1
double myList[10];

1
dataType arrayName[arraySize] = {value0, value1, ..., valuek};

1
double myList[4] = {1.9, 2.9, 3.4, 3.5}; // 与下列代码等价
2

3
double myList[4];
4
myList[0] = 1.9;
5
myList[1] = 2.9;
6
myList[2] = 3.4;
7
myList[3] = 3.5;

1
double mylist[4];
2
mylist = {1.9,2.9,3.4,3,5};

1
// Initializing Arrays with input value
2
const int ARRAY_SIZE = 10;
3
double myList[ARRAY_SIZE];
4
cout << "Enter" << ARRAY_SIZE << " values:";
5
for (int i = 0; i<ARRAY_SIZE;i++){
6
   cin >> myList[i];
7
}

1
// Printing arrays
2
for (int i = 0; i < ARRAY_SIZE; i++){
3
      cout << myList[i] << " ";
4
}

1
// Copying Arrays
2
for (int i = 0; i < ARRAY_SIZE; i++){
3
   list[i] = myList[i];
4
}

1
// Summing All Elements
2
double total = 0;
3
for (int i = 0; i < ARRAY_SIZE; i++){
4
    total += myList[i];
5
}

1
// Finding the Largest Element
2
double max = myList[0];
3
for (int i = 1; i < ARRAY_SIZE; i++){
4
    if (myList[i] > max)  max = myList[i];
5
}

1
// Finding the smallest index of the largest element
2
double max = myList[0];
3
int indexOfMax = 0;
4
for (int i = 1; i < ARRAY_SIZE; i++){
5
  if (myList[i] > max){
6
  max = myList[i];
7
    indexOfMax = i;
8
  }
9
}

1
elementType arrayName[rowSize][columnSize]; //注意是行在前，列在后

1
int matrix[5][5];

1
int array[][3] = { {1,2,3}, {4,5,6} }; // 多维数组必须从右往左保证后续维度已知

1
// Printing Arrays
2
for (int row = 0; row < rowSize; row++){
3
  for (int column = 0; column < columnSize; column++){
4
    cout << matrix[row][column] << " ";
5
  }
6
  cout << endl;
7
}

1
// Summing Elements by Column
2
for (int row = 0; row < rowSize; row++){
3
  for (int column = 0; column < columnSize; column++){
4
    cout << matrix[row][column] << " ";
5
  }
6
  cout << endl;
7
}

1
double scores[10][5][2];

1
int a[][2][3] = {
2
    { {1,2,3}, {4,5,6} },
3
    { {7,8,9}, {10,11,12} }
4
 // Right
5

6
int a[2][][3] = { { {1,2,3}, {4,5,6} } };  // Wrong
7
int a[][][3]  = { ... };                   // Wrong

1
string a = "apple";
2
string b = "banana";
3
if (a < b)
4
    cout << a << " comes before " << b << endl;

1
string s1 = "Hello";
2
string s2 = "Hi";
3
int result = s1.compare(s2);

1
dataType * pointerName;

1
int * pCount;

1
int count=5;
2
int *pCount = &count;
3

4
count++; //direct reference
5
(*pCount)++; //indirect reference

1
 int age;
2
 int *age_ptr = &age;
3

4
 age_ptr <=> &age
5
*age_ptr <=> age
6
*age_ptr = 50 <=> age = 50;
7
(*age_ptr)++ <=> age++;

1
int * p;
2
p = 0; // p has a null pointer value
3
p = NULL; or p = nullptr;//C++ 11

1
p±n;// move n*sizeof( pionter type)

1
int area = 1;
2
double *pArea = &area; // Wrong!

1
int *ptr1, *ptr2; //two pointers
2
int* ptr1, ptr2; // one pointer, one integer

1
int myList[10]; // myList <=> &myList[0]

1
int array[10];
2
int* ptr = array;
3
for (k=0; k<5; k++){
4
  cout<< *(ptr++); // Right
5
}
6
for (k=0; k<5; k++){
7
  cout<< *(array++); // Wrong
8
}

1
#include <iostream>
2
using namespace std;
3
int main(){
4
    int x[4] = {10,20,30,40};
5
    int *p = x; // p指向x[0]
6
    cout<<*++p<<endl;
7
    cout<<*p++<<endl;
8
    cout<<++*p<<endl;
9
    cout<<(*p)++<<endl;
10
    cout<<*p<<endl;
11
    return 0;
12
}

1
// 1.Using an array variable
2
char city[7] =  "Dallas";
3
char city[] =  {'D', 'a', 'l', 'l', 'a', 's', '\0' };
4
char city[] =  "Dallas";
5
cout << city;
6

7
//2.Declare a string variable using a pointer
8
const char *pCity = "Dallas";  //不能通过 pCity 修改它指向的字符串常量（存储在常量区）
9
cout<<pCity;

1
char city[10];
2
cin >>city; // Right; but only a word.stop at the first whitespace.
3

4
char *city2;
5
cin>>city2; //Wrong; No memory is allocated to store the content of city2.

1
cin.getline(char array[], int size, char delimitChar) // can read any character.
2
cin.getline(city,5,'\n') // example;

1
cout << "Enter a city: ";
2
cin >> city; // read to array city
3
cout << "You entered " << city << endl

1
returnValueType functionName(list of parameters){
2
    //function body;
3
}

1
int max(int num1 = 1, int num2 = 2){
2
    return (num1 > num2) ? num1 : num2;
3
}
4

5
max(2,1) // 传递，正常运算
6
max() // 未传递，使用默认值

1
#include <iostream>
2
using namespace std;
3
int v1 = 10;
4
int main(){
5
  int v1 = 5;
6
  cout << "local variable v1 is " << v1 << endl; // 5
7
  cout << "global variable v1 is " << ::v1 << endl; // 10
8
  return 0;
9
}

1
int n=5;
2
int &r=n;

1
#include <iostream>
2
using namespace std;
3
int main() {
4
  int i = 5;
5
  int& r = i; // r 是 i 的引用
6
  cout << "Value of i : " << i << endl; // 5
7
  cout << "Value of i reference : " << r << endl; // 5
8
  return 0;
9
}