4-14-多维数组、枚举、随机数、函数副本机制

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学习4-14期视频笔记

1、杨辉三角

#include<stdlib.h>#include<stdio.h>void main(){     #define n 10       int a[n][n] = { 0 };       for (int i = 0; i < n - 1; i++)       {              for (int j = 0; j <= i; j++)              {                     if (j==0||i == j)                     {                            a[i][j] = 1;                     }                     else                     {                            a[i][j] = a[i - 1][j- 1] + a[i - 1][j];                     }              }       }       for (int i = 0; i < n - 1; i++)       {              printf("%*d", 20 -2*i,a[i][0]);              for (int j = 1; j <= i; j++)              {                     printf("%4d",a[i][j]);              }              printf("\n");       }       system("pause");}

2、二维数组

//inta[3][4];

//&a[0][0]等同&a

//&a[i][0]等同&a[i]

//&a[i][j]等同a[i]+j

   for (int i = 0; i < 3; i++)       {              for (int j = 0; j < 4; j++)              {                     printf("%4d",a[i][j]= i *4 + j+1);              }              printf("\n");       }

//12 3 4

//56 7 8

//910 11 12

    //转置       for (int i = 0; i < 3; i++)       {              for (int j = 0; j < 4; j++)              {                     b[j][i] = a[i][j];               }       }

3、多维数组

多维数组在内存中位置是连续的

三维数组：

       int a[3][4][5] = {0};       for (int i = 0; i < 3; i++)       {              for (int j = 0; j < 4; j++)              {                     for (int k = 0; k < 5;k++)                     {                            a[i][j][k] = i * 4*5+ j*5 +k+ 1;                     }              }       }        //for (int i = 0; i < 60; i++)       //{       //     a[i/ 4 / 5][i % 20 / 5][i % 20 % 5] = i;       //}

多维数组的查找

4、枚举

   enum sex{man,women,weizhi};//0，1，2       for (enum sex a = man; a <=weizhi;a++)       {              printf("%d，",a);       }

输出结果：0，1，

5、生成随机密码

#include<stdlib.h>#include<stdio.h>#include<time.h> voidmain(){       time_t times;       srand((unsigned int)time(×));//取随机数种子       int length = rand() % 10 + 6;   //6-15位密码       char str[10] = {'a','b','c','d','e','f','g','h','e','j' };       for (int i = 0; i < length; i++)       {              int num = rand() % 10;              printf("%c", str[num]);       }       printf("\n");       system("pause");}

6、数组与函数

#include<stdlib.h>#include<stdio.h> //数组作为函数参数时会退化为指针，传递原地址，而不会创建副本void show(inta[10])//传递的是地址,数组是例外，//这里的inta[10]与int *a作用等同，可以相互替换{       printf("%p", &a);//与主函数的地址相同       printf("\n show=%d",sizeof(a));//4       int b[10] = { 0,1,2,3,4,5,6,7,8,9 };       printf("\n show=%d",sizeof(b));//40}void main(){       int a[10] = { 0,1,2,3,4,5,6,7,8,9 };       printf("%p", &a);       printf("%d", sizeof(a));//40       show(a);       system("pause");}

数组没有副本机制，

7、洗牌

#include<stdlib.h>#include<stdio.h>#include<time.h>void main(){       int a[54];       for (int i = 0; i < 54; i++)       {              printf("%d", a[i] = i);       }       srand((unsigned int)time(NULL));//随机数种子       for (int i = 0; i < 53; i++)       {              int num = i+rand()%(53-i);              int temp = a[i];              a[i] = a[num];              a[num] = temp;       }       printf("\n洗牌之后\n");       for (int i = 0; i < 54; i++)       {              printf("%d", a[i]);       }       system("pause");}

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