指针数组

指针数组就是元素类型为指针的数组，即带 * 的类型，因此指针数组一个元素占 4 字节

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char* arr[5] = {0};  //占4*5=20字节
		
arr[0] = (char*)1;  //int强制类型转换成char*
arr[1] = (char*)2;		
arr[2] = (char*)3;		
arr[3] = (char*)4;		
arr[4] = (char*)5;		

最常用的指针数组：

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char* p1 = "if";			
char* p2 = "for";			
char* p3 = "while";			
char* p4 = "switch";			
			
char* keyword[] = {p1,p2,p3,p4};			

等价于：

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char* keyword[] = {			
	"if",		
	"for",		
	"while",		
	"switch"		
};			

就是存的地址嘛，同理可以知道这个 keyword 的大小为 16

结构体指针

探测结构体指针的特性:

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struct Arg {		
   int a;		
   int b;		
   int c;		
};
int main(int argc, char* argv[]) {
  //带*宽度 ++ -- +整数 -整数 相减 比较大小 
  Arg* pArg;
  Arg* pArg2;
  
  pArg = (Arg*)100;
  
  pArg++;  //112，带*类型加减要看减去一个*后的大小，Arg三个int大小12
  pArg = pArg + 5;  //112+12*5=172
  
  pArg = (Arg*)100;
  pArg2 = (Arg*)20;
  int x = pArg - pArg2;
  printf("%d\n", x);  //(100-20)/12 = 6
  
  printf("%d\n", pArg); 
  return 0;
}

通过结构体指针读取、修改:

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struct Arg {		
   int a;		
   int b;		
   int c;		
};
int main(int argc, char* argv[]) {
  Arg s;
  s.a = 10;
  s.b = 20;
  s.c = 30;
  
  Arg* px = &s;
  
  printf("%d %d %d\n", px->a, px->b, px->c);  //结构体指针操作不能用.要用->
  
  px->a = 100;
  px->b = 200;
  px->c = 300;
  
  return 0;
}

课后作业

1. 创建一个 int* arr[5] 数组，并为数组赋值(使用&)

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   #include "stdafx.h" int main(int argc,char* argv[]) { int a = 1; int b = 2; int c = 3; int d = 4; int e = 5; int* arr[5] = {0}; arr[0] = &a; arr[1] = &b; arr[2] = &c; arr[3] = &d; arr[4] = &e; return 0; }

2. 创建一个字符指针数组，存储所有的 C 的关键词(查资料找)，并全部打印出来

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   #include "stdafx.h" int main(int argc,char* argv[]) { char* keyword[] = { "auto", "break", "case", "char", "const", "continue", "default", "do", "double", "else", "enum", "extern", "float", "for", "goto", "if", "int", "long", "register", "return", "short", "signed", "sizeof", "static", "struct", "switch", "typedef", "union", "unsigned", "void", "volatile", "while" }; for (int i = 0; i <32; i++) { printf("%s\n", *(keyword + i)); } return 0; }

3. 查找这些数据中，有几个 id=1 level=8 的结构体信息

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   0x00,0x01,0x02,0x03,0x04,0x05,0x06,0x07,0x07,0x09, 0x00,0x20,0x10,0x03,0x03,0x0C,0x00,0x00,0x44,0x00, 0x00,0x33,0x01,0x00,0x00,0x08,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x02,0x64,0x00,0x00,0x00,0xAA,0x00, 0x00,0x00,0x64,0x01,0x00,0x00,0x00,0x08,0x00,0x00, 0x00,0x00,0x02,0x00,0x74,0x0F,0x41,0x00,0x00,0x00, 0x01,0x00,0x00,0x00,0x05,0x00,0x00,0x00,0x0A,0x00, 0x00,0x02,0x57,0x4F,0x57,0x00,0x06,0x08,0x00,0x00, 0x00,0x00,0x00,0x64,0x00,0x0F,0x00,0x00,0x0D,0x00, 0x00,0x00,0x23,0x00,0x00,0x64,0x00,0x00,0x64,0x00

   结构体定义如下：

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   typedef struct TagPlayer { int id; int level; }Player;

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   #include "stdafx.h" char data[100] = { 0x00,0x01,0x02,0x03,0x04,0x05,0x06,0x07,0x07,0x09, 0x00,0x20,0x10,0x03,0x03,0x0C,0x00,0x00,0x44,0x00, 0x00,0x33,0x01,0x00,0x00,0x08,0x00,0x00,0x00,0x00, 0x00,0x00,0x00,0x02,0x64,0x00,0x00,0x00,0xAA,0x00, 0x00,0x00,0x64,0x01,0x00,0x00,0x00,0x08,0x00,0x00, 0x00,0x00,0x02,0x00,0x74,0x0F,0x41,0x00,0x00,0x00, 0x01,0x00,0x00,0x00,0x05,0x00,0x00,0x00,0x0A,0x00, 0x00,0x02,0x57,0x4F,0x57,0x00,0x06,0x08,0x00,0x00, 0x00,0x00,0x00,0x64,0x00,0x0F,0x00,0x00,0x0D,0x00, 0x00,0x00,0x23,0x00,0x00,0x64,0x00,0x00,0x64,0x00 }; typedef struct TagPlayer { int id; int level; } Player; int func(int id, int level) { int cnt = 0; for (int i = 0; i < 100 - 7; i++) { Player* pdata = (Player*)(data + i); if (pdata->id == id && pdata->level == level) cnt++; } return cnt; } int main(int argc,char* argv[]) { int num = func(1, 8); printf("%d\n", num); return 0; }