C语言基础知识

1.数据类型部分

   1.1简单又简单的数据运算和输出

        /* 定义变量并赋初值 */

        int    a = 5;      

       char   c = 'a';  

       float f = 5.3;    

       doublem = 12.65;

       doubleresult;

        

         /* 同类型数据间进行运算并输出结果 */

         printf("a + c = %d/n", a + c);

         printf("a + c = %c/n", a + c);//按照ASCII数值计算只不过输出形式不一样而已

         printf("f + m = %f/n", f + m);

 

         /* 不同类型数据间进行运算并输出结果 */

         printf("a + m = %f/n", a + m);

         printf("c + f = %f/n", c + f);

 

         /* 将上述四个变量进行混合运算，并输出结果 */

         result = a + c * (f + m);

         printf("double = %f/n", result);

         getch();

   1.2格式化输出一下
         

        /* 换行符'/n'，用于输出换行 */

         printf("How are you?/n");

         printf("I am fine./n/n");

 

         /* 横向跳格符'/t'，使跳到下一个输出区 */

         printf("How are you?/t");

         printf("I am fine./n/n");

 

         /* 退格符'/b'，使当前的输出位置退一格，即输出的起始位置左移一位 */

         printf(" How are you?/n");

         printf(" /bI am fine./n/n");

 

         /* 回车符'/r'，使当前输出位置回到本行开头 */

         printf("                I am fine.");

         printf("/rHow are you?/n/n");

 

         /* 多个转义字符的混合运用 */

         printf("note:/n a s/ti/b/bk/rp/n");

  1.3简单的bool运算
   

        /* 定义一个整数类型的变量，用来存放后面算式的值 */

         int logic;   

 

         inta = 1;

         int b = 2;

         int c = 3;

 

         logic = a+b>c&&b<=c;

         printf("logic = %d/n", logic);

 

         logic = a>=b+c||b==c;

         printf("logic = %d/n", logic);

 

         logic = !(a<c)+b!=1&&(a+c)/2;

         printf("logic = %d/n", logic);

         getch();

 
   1.4 ++和--总是不清楚
    
  

         inti, j, k;

         int m, n, p;

 

         i = 8;

         j = 10;

         k = 12;

   

         /* 自增在操作数之前 */

         m = ++i;

        printf("i = %d/n", i);

         printf("m = %d/n", m);

 

         /* 自减在操作数之后 */

         n = j--;

         printf("j = %d/n", j);

         printf("n = %d/n", n);

 

         /* 自增、自减的混合运算 */

         p = (++m)*(n++)+(--k);

         printf("k = %d/n", k);         

         printf("p = %d/n", p);        

         getch();

  1.5 与或非一下
   

         /* 定义了一个无符号字符型变量，此变量只能用来存储无符号数 */

         unsigned char result;

   

         inta, b, c, d;

         a = 2;

         b = 4;

         c = 6;

         d = 8;

 

         /* 对变量进行“按位与”操作 */

         result = a & c;

         printf("result = %d/n", result);

 

         /* 对变量进行“按位或”操作 */

         result = b | d;

         printf("result = %d/n", result);

 

         /* 对变量进行“按位异或”操作 */

         result = a ^ d;

         printf("result = %d/n", result);

 

         /* 对变量进行“按位取反”操作 */

         result = ~a;

         printf("result = %d/n", result);

         getch();

  
   1.6 左右移

    unsigned a, b, c, d;

         intn;

 

         a = 64;

         n = 2;

 

         /* 将操作数a右移(6-n)位 */

         b = a >> (6-n);

         printf("b = %d/n", b);

 

         /* 将操作数a左移n位 */

         c = a << n;

         printf("c = %d/n", c);

 

         /* 对操作数a进行的混合位运算 */

         d = (a >> (n-1)) | (a << (n+1));

         printf("d = %d/n", d);

         getch();

  1.7 可恨又可爱的指针
   

        /* 定义整形指针 */

        intbegin=0, end=0;
        int *p1=0;
        const int* p2=0;
        int* const p3=&begin;
        const int* const p4=&end; 
         begin = 10;

         /* 让人头晕的赋值 */

         p1 = &begin;

         end = *p1;

         *p2=1;//Error
         *p3=1;//OK
         p2=&end;//ok
         p3=&end;//Error
         *p4=1//Error
         p4=&end;//Error

         printf("begin = %d/n", begin);

         printf("end = %d/n", end);

 

         /* 输出指针中的地址值 */

         printf("p 1= %d/n", p1);

         printf("&begin = %d/n", &begin);

         printf("*p 1= %d/n", *p1);

         getch();

  1.8 大公约和小公倍
     
    intx, y, num1, num2, temp;

         printf("请输入两个正整数：/n");

         scanf("%d %d", &num1, &num2);

 

         if(num1 < num2)

         {

                   temp = num1;

                   num1 = num2;

                   num2 = temp;

         }

         x = num1;

         y = num2;

         while(y != 0)

         {

                   temp = x%y;printf("%d/n", temp);

                   x = y;

                   y = temp;

         }

         printf("它们的最大公约数为：%d/n", x);

         printf("它们的最小公倍数为：%d/n", num1*num2/x);

         getch();

   1.9 矩阵转置
 
    voidconvert(intelement[N][N])

        {

            inti, j, t;

            for(i=0; i<N; i++)

                  for(j=i+1; j<N; j++)

                   {

                            t = element[i][j];

                            element[i][j] = element[j][i];

                            element[j][i] = t;

                   }

         }

 
   1.10 命令行参数

   voidmain(intargc, char* argv[])

        {

           intdisp, count;

 

          if(argc < 2)

          {

                  printf("You must enter the length of the count/n");

                  printf("on the command line. Try again/n");

                   exit(1);    /* 非正常跳出程序 */

          }

 

          if(argc==3 && !strcmp(argv[2], "display"))

                   disp = 1;

          else

                   disp = 0;

          for(count = atoi(argv[1]); count; --count)

                   if(disp)

                            printf("%d/n", count);

 

          putchar('/a');    /* 将产生蜂鸣 */

          printf("Down");

          getch();

          return;

      }

   

  1.11 查找字符串原来是这样

     intfind_substr(char* s1, char* s2)

    {

         registerintt;

         char *p, *p2;

 

        for(t=0; s1[t]; t++)

         {

                   p = &s1[t];

                   p2 = s2;

 

                  while(*p2 && *p2==*p)

                   {

                            p++;

                            p2++;

                   }

                   if(! *p2)

                            returnt;

         }

         return -1;

     }

  1.12 也算年月日
             

      /* 给出年、月、日，计算该日是该年的第几天 */

     # include <stdio.h>

     # include <conio.h>

 

    intsum_day(intmonth, intday);

    intleap(intyear);

 

    voidmain()

    {

         intyear, month, day;

         intdays;

         printf("请输入日期(年，月，日)：");

         scanf("%d, %d, %d", &year, &month, &day);

         printf("%d年%d月%d日", year, month, day);

         days = sum_day(month, day);    /* 调用函数sum_day() */

         if(leap(year) && month>=3)    /* 调用函数leap() */

                   days = days + 1;

         printf("是该年的第%d天./n", days);

         getch();

   }

 

    /* 定义静态存储变量并赋初值 */

   staticintday_tab[13] = {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};

 

    intsum_day(intmonth, intday)    /* 计算日期 */

    {

         inti;

         for(i=1; i<month; i++)

                   day = day + day_tab[i];

         returnday;

    }

 

    intleap(intyear)

   {

         intleap;

         leap = (year%4==0&&year%100!=0)||(year%400==0);

         returnleap;

    }

    1.13 插入字符
                              

       # include <stdlib.h>

       # include <string.h>

       # include <stdio.h>

 

      voidmain()

      {

         /* 声明子函数 */

         intbinary(char *ptr[], char *str, intn);    /* 查找函数声明 */

         voidinsert(char *ptr[], char *str, intn, inti);    /* 插入函数声明 */

 

         char *temp, *ptr1[6];

         inti;

         printf("请为字符形指针数组赋初值：/n");

         for (i=0; i<5; i++)

         {

                   ptr1[i] = (char *)malloc(20);    /* 为指针分配地址后 */

                  gets(ptr1[i]);    /* 输入字符串 */

         }

         ptr1[5] = (char *)malloc(20);

         printf("/n");

 

         printf("original string:/n");

         for(i=0; i<5; i++)    /* 输出指针数组各字符串 */

                  printf("%s/n", ptr1[i]);

 

         printf("/ninput search string:/n");

         temp = (char *)malloc(20);

         gets(temp);    /* 输入被插字符串 */

 

         i=binary(ptr1, temp, 5);    /* 寻找插入位置i */

         printf("i = %d/n", i);

 

         insert(ptr1, temp, 5, i);    /* 在插入位置i处插入字符串 */

         printf("output strings:/n");

 

         for(i=0; i<6; i++)    /* 输出指针数组的全部字符串 */

                  printf("%s/n", ptr1[i]);

    }

 

       intbinary(char *ptr[], char *str, intn)

      {

         /* 折半查找插入位置 */

         inthig, low, mid;

         low = 0;

         hig = n-1;

         if(strcmp(str,ptr[0]) < 0)

                   return 0;

        /* 若插入字符串比字符串数组的第0个小，则插入位置为0 */

         if(strcmp(str,ptr[hig]) > 0)

                   returnn;

        /* 若插入字符串比字符串数组的最后一个大，则应插入字符串数组的尾部 */

        while(low <= hig)

         {

                   mid = (low + hig)/2 ;

                   if (strcmp(str,ptr[mid]) < 0)

                            hig = mid - 1;

                   elseif(strcmp(str,ptr[mid]) > 0)

                            low = mid + 1;

                   else

                            returnmid;    /* 插入字符串与字符串数组的某个字符串相同 */

          }

          returnlow;    /* 插入的位置在字符串数组中间 */

     }

 

      voidinsert(char *ptr[], char *str, intn, inti)

      {

         intj;

         for(j=n; j>i; j--)    /* 将插入位置之后的字符串后移 */

                  strcpy(ptr[j], ptr[j-1]);

         strcpy(ptr[i], str);    /* 将被插字符串按字典顺序插入字符串数组 */

      }