C程序设计进阶

Week2

r = sqrt(100.0);
k = pow(x,y);
i = strlen(str1);
v = strcmp(str1,str2);
n = atoi(str1);

数组的名字 = 数组的地址
int a[2];
cout << a <<endl;  //a is the address of a array

Week4 Pointer note:

取地址运算符：“&”

int c = 76;
cout<<&c<<endl;
cout<<sizeof(&c)<<endl; //4 bytes

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int c = 76;
int *pointer; //定义名字为pointer的指针变量
pointer = &c; //将变量c的地址赋值给指针变量pointer
              //赋值后，称指针变量pointer指向了变量c

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int c = 76;
int *pointer = &c;
*pointer:所指向的存储单元的内容：变量c

 — — — — — — — — — — — — 

#include<iostream>
using namespace std;
int main() {
int iCount = 18;
int *iPtr = &iCount;
*iPtr = 58;
cout << iCount << endl;
cout << iPtr << endl;
cout << &iCount << endl;
cout << *iPtr << endl;
cout << &iPtr << endl;
return 0;
}

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#include<iostream>
using namespace std;
int main() {
int a = 0, b = 0, temp;
int *p1 = NULL, *p2 = NULL;
cin >> a >> b;
p1 = &a;
p2 = &b;
if (*p1 < *p2)
{
temp = *p1; *p1 = *p2; *p2 = temp;
}
cout << "max= " << *p1 << ",min= " << *p2 << endl;
return 0;
}

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运算符优先级：后置++ -- 高于 （前置++-- 逻辑非 （!）* & ) 从右到左

#include<iostream>
using namespace std;
int main() {
int a[5] = { 1,2,3,4,5 };
int *p = &a[3];
cout << *p << endl;
*p = 100;
cout << a[3] << endl;
return 0;
}

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#include<iostream>
using namespace std;
int main() {
 int a[5] = { 1,2,3,4,5 };
 cout << a << endl;
 cout << *a << endl;
 cout << &a[0] << endl;
 cout << a[0] << endl;
 return 0;
}

#include<iostream>
#include<iomanip>
using namespace std;
int main() {
 int a[10], *p = NULL, *q = NULL, temp;
 for (p = a; p < a + 10; p++)
  cin >> *p;
 for (p = a, q = a + 9; p < q; p++, q--) {
  temp = *p; *p = *q; *q = temp;
 }
 for (p = a; p < a + 10; p++)
  cout << setw(3) << *p;
 return 0;
}

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#include<iostream>

using namespace std;
int main() {
 int a[3][4] = { 1,2,3,4,5,6,7,8,9,10,11,12 };
 int(*p)[4], i, j;
 p = a;
 cin >> i >> j;
 cout << *(*(p + i) + j) << endl; .

return 0;
}

Week5: 

char c[6]={'h','e','l','l','o','\0'}
char *pc = c;
cout<<c<<endl;  //hello
cout<<pc<<endl; //hello

cout<<static_cast<void*>(c)<<endl;  //address
cout<<static_cast<void*>(pc)<<endl; //address

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#include<iostream>
using namespace std;
int main() {
 char buffer[10] = "ABC";
 char *pc;
 pc = "hello";
 cout << pc << endl;
 pc++;
 cout << pc << endl;
 cout << *pc << endl;
 pc = buffer;
 cout << pc;
 return 0;
}
output:
hello
ello
e
ABC

Week 7:

Struct: 结构体数据类型的特性与普通数据类型的特性是一致的。

#include<iostream>
using namespace std;

struct student {
 int id_num;
 char name[10];
};

void renew(student *one) {
 one->id_num = 20130000 + one->id_num; //one->id_num is equivalent to (*one).id_num
 for (int i = 0; one->name[i] != '\0'; i++)
  one->name[i] = toupper(one->name[i]);
}

int main() {
 student mike = { 123,{'m','i','k','e','\0'} };
 renew(&mike);
 cout << mike.id_num << " " << mike.name;
 return 0;
}

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#include<iostream>
using namespace std;

struct student {
 int id_num;
 char name[10];
};

int main() {
 student myclass[3] =
 { 123,{'m','i','k','e','\0'},
   133,{'t','o','m','\0'},
   143,{'j','a','c','k','\0'} };
 student *one = myclass;
 cout << (*one).id_num << " " << (*one).name << endl;
 one++;
 cout << one->id_num << " " << one->name << endl;
 return 0;
}

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LinkedList: 

Creation:

#include<iostream>
using namespace std;

struct student {
 int id;
 student *next;
};

student *create() {
 student *head, *temp; int num, n = 0;
 head = new student;
 temp = head;
 cin >> num;
 while (num != -1) {
  n++;
  temp->id = num;
  temp->next = new student;
  temp = temp->next;
  cin >> num;
 }
 if (n == 0)head = NULL; else temp->next = NULL;
 return head;
}

int main() {
 return 0;
}

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Delete

student *dele(student *head, int n) {
 student *temp, *follow;
 temp = head;
 if (head == NULL) {
  return head;
 }
 if (head-> num == n) {
  head = head->next;
  delete temp;
  return(head);
 }
 while (temp != NULL&&temp->num != n) {
  follow = temp;
  temp = temp->next;
 }
 if (temp == NULL)
  cout << "not found";
 else {
  follow->next = temp->next;
  delete temp;
 }
 return head;

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Insert:

#include<iostream>
using namespace std;

struct student {
 int id,num;
 student *next;
};

student *create() {
 student *head, *temp; int num, n = 0;
 head = new student;
 temp = head;
 cin >> num;
 while (num != -1) {
  n++;
  temp->id = num;
  temp->next = new student;
  temp = temp->next;
  cin >> num;
 }
 if (n == 0)head = NULL; else temp->next = NULL;
 return head;
}

student *dele(student *head, int n) {
 student *temp, *follow;
 temp = head;
 if (head == NULL) {
  return head;
 }
 if (head-> num == n) {
  head = head->next;
  delete temp;
  return(head);
 }
 while (temp != NULL&&temp->num != n) {
  follow = temp;
  temp = temp->next;
 }
 if (temp == NULL)
  cout << "not found";
 else {
  follow->next = temp->next;
  delete temp;
 }
 return head;
}

student *insert(student *head, int n) {
 student *temp, *unit, *follow;
 temp = head; unit = new student;
 unit->num = n; unit->next = NULL;
 if (head == NULL) {
  head = unit;
  return(head);
 }
 while ((temp->next != NULL) && (temp->num < n)) {
  follow = temp; temp = temp->next;
 }
 if (temp == head) {
  unit->next = head; head = unit;
 }
 else {
  if (temp->next == NULL)temp->next = unit;
  else {
   follow->next = unit; unit->next=temp;
  }
 }
 return(head);
}

int main() {
 student *pointer = create();
 while (pointer->next!=NULL)
 {
  cout << pointer->id << endl;
  pointer = pointer->next;
 }
 return 0;
}

#include <iostream>
#include <cstring>
using namespace std;

int m, n;//n行m列
char map[101][101];//地图矩阵
int already[101][101];//已走地图记忆
int min_count = 0;

void cross(int u, int v, int i, int j)
{
 int t = already[u][v];
 if (u == i && v == j)//起点即为到达终点
 {
  min_count = t;
 }
 t++;

if (v < m - 1 && map[u][v + 1] != '#'  && already[u][v + 1]>t)//在迷宫内、右侧非墙且此点没有走过
 {
  already[u][v + 1] = t;//标记此点为第t步
  cross(u, v + 1, i, j);//以此点为起点继续走
 }
 if (u > 0 && map[u - 1][v] != '#'  && already[u - 1][v]>t)
 {
  already[u - 1][v] = t;
  cross(u - 1, v, i, j);
 }
 if (v > 0 && map[u][v - 1] != '#'  && already[u][v - 1]>t)
 {
  already[u][v - 1] = t;
  cross(u, v - 1, i, j);
 }
 if (u < n - 1 && map[u + 1][v] != '#' && already[u + 1][v]>t)
 {
  already[u + 1][v] = t;
  cross(u + 1, v, i, j);
 }
}

int main() {
 int startx, starty, endx, endy;
 cin >> n >> m;
 for (int i = 0; i<n; i++) {
  for (int j = 0; j<m; j++) {
   cin >> map[i][j];
   if (map[i][j] == 'S') {
    startx = i;
    starty = j;
   }
   if (map[i][j] == 'T') {
    endx = i;
    endy = j;
   }
  }
 }
 memset(already, 1, sizeof(already));
 already[startx][starty] = 0;
 cross(startx, starty, endx, endy);
 cout << min_count << endl;
 return 0;
}

C++ 引用 vs 指针
引用很容易与指针混淆，它们之间有三个主要的不同：

不存在空引用。引用必须连接到一块合法的内存。
一旦引用被初始化为一个对象，就不能被指向到另一个对象。指针可以在任何时候指向到另一个对象。
引用必须在创建时被初始化。指针可以在任何时间被初始化。

#include <iostream>
 
using namespace std;
 
int main ()
{
   // 声明简单的变量
   int    i;
   double d;
 
   // 声明引用变量
   int&    r = i;
   double& s = d;
   
   i = 5;
   cout << "Value of i : " << i << endl;
   cout << "Value of i reference : " << r  << endl;
 
   d = 11.7;
   cout << "Value of d : " << d << endl;
   cout << "Value of d reference : " << s  << endl;
   
   return 0;
}