目录
1,initialization of one-dimensional arrays
2，algorithm：bubble sort algorithm(起泡排序in Chinese)
P.S. why does it called"bubble sort"?
2,Define and reference two-dimensional arrays(matrix)
5,some functions for string manipulating
1,the functions below should be referenced
reasons：it is really inconvenient to define mutiple variblle
solution：You can store multiple variables of the same type in an array data structure
int a[10];
//10 :the element numbers in the arrayE.g.
/*Assign the values of 10 array elements to 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, and require the output in reverse order*/ #include<stdio.h> int main() { int i,a[10]; for(i=0;i<=9;i++) { a[i]=i; } for(i=9;i>=0;i--) { printf("%d\n",a[i]); } return 0; }Arrays always start at zero.
1,initialization of one-dimensional arrays
1,syntax:
int a[5]={1,2,3,4,5};2,some rules
1，the elements in an array are assigned sequentially
2，C# default unsigned varialble to null
3，you can even just default the length of an array,if you assigned all of the elements
2，algorithm：bubble sort algorithm(起泡排序in Chinese)
eg.there are 10 places which is distinct in size,you need sort them from the smallest to the largest.
//there are 10 places which is distinct in size,
//you need sort them from the smallest to the largest.
#include<stdio.h>
int main()
{
int i,j,k,a[10];
printf("plz input 10 numbers")
for(i=0;i<10;i++)
{
scanf("%d\n",a[i]);
}
for(i=0;i<10;i++)
for(j=0;j=9-i;j++)
{
if(a[i]>a[i+1])
{
t=a[i];
a[i]=a[i+1];
a[i+1]=t
}
}
printf("the sorted numbers is:\n")
for(i=0;i<10;i++)
printf("%d\n",a[i])
return 0;
}P.S. why does it called"bubble sort"?
i think it is because every time the elements are compared with adjacent one from front ro back ,and the larger one gradually moved to the back just like "bubbles".
2,Define and reference two-dimensional arrays(matrix)
1,define the type of a matrix
float a[3][4]a=
a[0] —— a[0][0] a[0][1] a[0][2] a[0][3]
a[1] —— a[1][0] a[1][1] a[1][2] a[1][3]
a[2] —— a[2][0] a[2][1] a[2][2] a[2][3]
2, initialization of matrix
1,syntax
int a[3][4]={
{1,2,3,4},{5,6,7,8},{9,10,11,12}};
or
int a[3][4]={1,2,3,4,5,6,7,8,9,10,11,12};
2,some tips:
1,Then the length of dimension 1 can be unassigned when defining the array, but the length of dimension 2 cannot be omitted.
2,You can assign initial values to some elements you want.
just like
int a[3][4]={
{1},{0,6},{0,0,11}}3,Multidimensional array
float a[2, 3, 4];the order of it:
a[0][0][0] → a[0][0][1] → a[0][0][2] → a[0][0][3] →
a[0][1][0] → a[0][1][1] → a[0][1][2] → a[0][1][3] →
a[0][2][0] → a[0][2][1] → a[0][2][2] → a[0][2][3] →
a[1][0][0] → a[1][0][1] → a[1][0][2] → a[1][0][3] →
a[1][1][0] → a[1][1][1] → a[1][1][2] → a[1][1][3] →
a[1][2][0] → a[1][2][1] → a[1][2][2] → a[1][2][3]4,character array
1,sample:
char a[10];int i;
a[0]='f';a[1]='u';a[2]='c';a[3]='k';
for(i=0,i<4,i++)
printf("%c",a[i]);char c[]={′f′,′ ′ ,′u′,′c′,′ ′,′k′,′y′,′o′,′u′};Generally, strings are terminated with a null character (ASCII code 0). This allows functions (like Serial.print ()) to tell where the end of a string is.
5,some functions for string manipulating
1,the functions below should be referenced
#include<string.h>2,puts
you can use function <puts> to output an string array.
#include <stdio.h>
int main()
{
char str[]={"a\nb"};
puts(str);
return 0;
}
>>
a
b3，gets(不用调用string.h
and also , you can input some string in to the array.
E.G.
#include<stdio.h>
int main()
{
char string[100];
gets(string);
}4,strcat
you can use fun. strcat to connect two string array.（注意内存问题）
#include<stdio.h>
#include<string.h>
int main()
{
char str1[30] = { "hello " };
char str2[] = { "world" };
strcat_s(str1, str2);
printf("%s", str1);
return 0;
}>>
hello world例题：
C、 char str[10], *st="abcde"; strcat(str, st);
D、 char str[10]="", *st="abcde"; strcat(str, st);D正确 ，必须初始化
5,strcpt
this function allow you to copy elements from one array to another.
E.G.
char str1[10], str2[]="a";
strcpy(str1, str2);
//or
// strcpy(str1, "a");
6,strcmp
that function let you compare ascll value between two arrays
(from front to back)
1,syntax
strcmp(str1, str2);
strcmp("a", "b");
strcmp(str1, "b");
2,for the result
--if the char arrays is absolutely the same:it returns 0
--it is different:
1,a>b: return 1
2,a<b:return -1
7,strlen
to get the length of a character array. before'\0'
#include <stdio.h>
#include <string.h>
int main()
{
char str[10]="a";
printf("%d,%d\n",strlen(str),strlen("a"));
}
>>
0.5,0.58,strlwr/strupr
to change low-case letters to capitals
-----strupr
to change capitals to low-case letters
-----strlwr