学习内容：
-
命名空间
-
指针与动态分配内存
-
引用与指针传参、返回指针、递归、函数默认值、重载的使用
-
掌握C++11的基础语言扩展机制(auto类型推导、统一初始化、范围循环等)
-
了解string和vector的基础应用
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实习任务一 ：myNamespace
#include <iostream>
using namespace std;
namespace myNspace{
void swap(int &a, int &b){
int temp = a;
a = b;
b = temp;
}
}
namespace myNspace2{
void swap(int *a,int *b){
int temp = *a;
*a = *b;
*b = temp;
}
}
int main()
{
int m = 1, n= 2;
cout<<"m = "<<m<<endl;
cout<<"n = "<<n<<endl<<endl;
myNspace::swap(m,n);//这是用取地址的方法
cout<<"m = "<<m<<endl;
cout<<"n = "<<n<<endl<<endl;
myNspace2::swap(&m,&n);//这是用指针的方法
cout<<"m = "<<m<<endl;
cout<<"n = "<<n<<endl;
return 0;
}
运行结果：
m = 1
n = 2
m = 2
n = 1
m = 1
n = 2
[Finished in 0.3s]
-
实习任务二 ： getMax
#include <iostream>
using namespace std;
int *getMax(int *a, int size){
int *max = new int(0);
for(int i =0;i<size;i++){
if(*max < *(a+i)){
*max = *(a+i);
}
}
cout<<max<<endl;
return max;
}
int main()
{
int a[8] = {1,2,43,3,5,6,7};
int * temp = getMax(a,7);
cout<<temp<<endl;
cout<<*temp<<endl;
delete temp;//函数返回一个指针，函数中的指针在函数外销毁
return 0;
}
运行结果：
0x7fcc8cc025c0
0x7fcc8cc025c0
43
[Finished in 0.3s]
-
实习任务三 ：getDiagonal
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指针版
#include <iostream>
#include <iomanip>
#include <vector>
using namespace std;
void print2Darray(int** array, int size){
for(int i =0;i<size;i++){
for(int j =0;j<size;j++){
cout<<setw(4)<<array[i][j];
}
cout<<endl;
}
cout<<endl;
}
int * getDiagonal(int** matrix, int n){
int *diag = new int[100];
for(int i=0;i<n;i++){
*(diag+i) = *(*(matrix+i)+i);
}
return diag;
}
int main(){
int** matrix = new int*[10];
for(int i=0;i<10;i++){
*(matrix+i) = new int[10];
}
int x = 1;
for(int i=0;i<10;i++){
for(int j=0;j<10;j++){
*(*(matrix+i)+j) = x;
++x;
}
}//初始化指针数组
print2Darray(matrix,10);
int* p = getDiagonal(matrix, 10);
cout<<"Diag of the matrix:"<<endl;
for(int i =0;i<10;i++){
cout<<setw(4)<<*(p+i);
}
cout<<endl;
for(int i =0;i<10;i++){
delete [] *(matrix+i);
}
delete [] matrix;
//这两步很关键，出来混迟早要还的 ：）
//要delete数组的每一行行地址还有数组指向这些行的首地址
return 0;
}
运行结果：
1 2 3 4 5 6 7 8 9 10
11 12 13 14 15 16 17 18 19 20
21 22 23 24 25 26 27 28 29 30
31 32 33 34 35 36 37 38 39 40
41 42 43 44 45 46 47 48 49 50
51 52 53 54 55 56 57 58 59 60
61 62 63 64 65 66 67 68 69 70
71 72 73 74 75 76 77 78 79 80
81 82 83 84 85 86 87 88 89 90
91 92 93 94 95 96 97 98 99 100
Diag of the matrix:
1 12 23 34 45 56 67 78 89 100
[Finished in 0.3s]
-
vector版
#include <iostream>
#include <vector>
#include <iomanip>
using namespace std;
vector<int> getDiagonal(const vector<vector<int> > & matrix){
vector<int> a;//vector的好处：不用预先定义大小
for(int i=0;i<matrix.size();i++){
a.push_back(matrix[i][i]);
}
return a;
}
int main()
{
vector< vector<int> > matrix(9, vector<int>(10));//定义一个二维向量（数组）
int x = 1;
for(int i=0;i<matrix.size();i++){
for(int j=0;j<matrix[i].size();j++){
matrix[i][j] = x;
cout<<setw(3)<<x;
x++;
}
cout<<endl;
}
cout<<endl;
vector<int> m;
m = getDiagonal(matrix);
vector<int>::iterator it;
for(vector<int>::iterator i=m.begin();i!=m.end();i++){
cout<<setw(3)<<*i;
}
return 0;
}
运行结果：
1 2 3 4 5 6 7 8 9 10
11 12 13 14 15 16 17 18 19 20
21 22 23 24 25 26 27 28 29 30
31 32 33 34 35 36 37 38 39 40
41 42 43 44 45 46 47 48 49 50
51 52 53 54 55 56 57 58 59 60
61 62 63 64 65 66 67 68 69 70
71 72 73 74 75 76 77 78 79 80
81 82 83 84 85 86 87 88 89 90
1 12 23 34 45 56 67 78 89
[Finished in 0.4s]
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实习任务四：四则运算
#include <iostream>
#include <ctime>
using namespace std;
int add(int a,int b){
return a+b;
}
int sub(int a,int b){
return a-b;
}
int multiply(int a,int b){
return a*b;
}
int devide(int a, int b){
return a/b;
}
char menu(){
char choice;
cout<<"1) add two numbers\n";
cout<<"2) sub two numbers\n";
cout<<"3) multiply two numbers\n";
cout<<"4) devede two numbers\n";
cout<<"0) quit\n";
cout<<"Enter your choice:\n";
cin>>choice;
return choice;
}
bool answerQuestion(int num1,int num2,int (*f)(int ,int ), int answer ){
return f(num1,num2)==answer;
}
int main()
{
int x_c = 0, x_w = 0;//answer correct & wrong counter
while(true) {
char choice=menu();
if(choice=='0')
break;
int num1, num2;
num1=rand()%90+10;
num2=rand()%90+10;
decltype(add) *pf; //add函数的类型
char op;
switch(choice){
//得到 10~99 的整数
case '1':pf=add; //add函数的类型给了pf
op='+';
break;
case '2':pf=sub;
op='-';
break;
case '3':pf=multiply;
op='*';
break;
case '4':pf=devide;
op='/';
break;
default :continue;
}
if(op=='/'){
while(num1<=num2||num1%num2!=0){
num1=rand()%90+10;
num2=rand()%90+10;
}
}
int answer;
cout<<num1<<op<<num2<<"=?";
cin>>answer;
if(answerQuestion(num1, num2,pf,answer)==true){
x_c++;
cout<<"Correct!"<<endl;
}
else{
if(x_w==3)
break;
x_w++;
cout<<"Wrong!"<<endl;
}
}
cout<<"The number of your correct answers is "<<x_c<<endl;
cout<<"The number of your wrong answers is "<<x_w<<endl;
return 0;
}
-
课后练习
- 默认参数
#include <iostream>
using namespace std;
int sum( int a, int b=1, int c=3 ){
return a+b+c;
}
int main()
{
//try comment the code below and see what happens
int sum(int a, int b=3, int c=4);
cout<<sum (2)<<endl;
cout<<sum (2,5)<<endl;
cout<<sum (2,3,6)<<endl;
return 0;
}
- 函数引用？
#include <iostream>
using namespace std;
char & elem(char *s, int n){
return s[n]; //传出来的是char&型
}
int * add(int a, int b){
int *c = new int(a+b);
return c;//传出来的是int*型
}
int main(){
char str[]="HelloWorld";
cout<<elem(str,1)<<endl;
elem(str,1)= 'A'; //&str[1] = 'A'?
cout<<elem(str, 1)<<endl;
cout<<str<<endl;
int * k;
k = add(1,2);
cout<<*k<<endl;
delete k;
return 0;
}
- 作用域
#include <iostream>
using namespace std;
int x = 10;
int main()
{
int x = 15;
cout<<x<<endl;
cout<<::x<<endl;
return 0;
}
- exchanging numbers not working
#include <iostream>
using namespace std;
void xhg(int *a,int *b){
int *tmp;
tmp=b;
b=a;
a=tmp; //仅仅交换了a和b代表的地址，地址指向的东西没有变
cout<<*a<<' '<<*b<<endl;
}
void xhg2(int *a, int*b){
int tmp;
tmp = *b;
*b = *a;
*a = tmp;
cout<<*a<<' '<<*b<<endl;
}
int main()
{
int x(5),y(4);
xhg(&x,&y);
cout<<x<<' '<<y<<endl;
xhg2(&x,&y);
cout<<x<<' '<<y<<endl;
return 0;
}
- 递归求和
#include <iostream>
using namespace std;
int ff(int *a,int size){
if(size==1)
return a[0];
return a[size-1]+ff(a,size-1);
}
int main()
{
int a[5]={1,2,3,4,5};
cout<<"result: "<<ff(a,5)<<endl;
return 0;
}
- 递归逆序输出字符串
#include <iostream>
using namespace std;
void f(const string& s,int n){
cout<<s[n-1];
if(n>1)
f(s,n-1);
}
int main(){
f("animal",6);
cout<<endl;
f("hello",3);
return 0;
}
- 寻找数组最大值和最小值之间的差
#include <iostream>
using namespace std;
int func(int data[],int size){
int a=data[0];
int b=data[0];
for(int i=1;i<size;++i) {
if(data[i]>a)
a=data[i];
if(data[i]<b)
b=data[i];
}
return a-b;
}
int main()
{
int a[] = {9,3,2,-1,8,0,4};
cout<<func(a,7)<<endl;
cout<<func(a+2,4)<<endl;
return 0;
}
- sum from 1 to 100 at the interval of x
#include <iostream>
using namespace std;
int fun(int interval=1){
int sum=0, i=0;
for(i=0; i<100; i+=interval)
sum+=i;
return sum;
}
int main()
{
cout<<"Result1: "<<fun(2)<<endl;
cout<<"Result2: "<<fun()<<endl;
return 0;
}
9.calculate the average number of the fist n numbers of the array
#include <iostream>
using namespace std;
double func( double pData[], int size);
int main(){
double array[] = {2.2, 3.8, 6, 5.4};
cout<<"Result: "<<func(array, 4)<<endl;
cout<<"Result: "<<func(array, 3)<<endl;
return 0;
}
double func( double pData[], int size){
double result=0;
int i;
for(i=0; i<size; ++i) {
result+=pData[i];
}
result /= size;
return result;
}
- vector iteration
#include <iostream>
#include <vector>
using namespace std;
int main(){
vector<int> vec{2,4,5,6,10,15,3,21,36,72,9,13};
for(int i=0;i<vec.size();++i)
cout<<vec[i]<<" ";
cout<<endl;
for(auto it=vec.begin ();it!=vec.end ();++it)
cout<<*it<<" ";
cout<<endl;
for(auto e : vec)
cout<<e<<" ";
cout<<endl;
return 0;
}
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