15-week job (two-dimensional array)

Summary of learning content this week

1. Two-dimensional array


1). Definition and reference of two-D arrays


• Defined
  Type an array group name [President degree] [column length]

  int a[3][2];
  Defines a two-dimensional array a,3 rows 2 columns, 6 elements

  int b[5][10];
  Defines a two-dimensional array b,5 rows 10 columns, 50 elements

• Reference
  Define first, then use
  References to array elements:
  Array name [row subscript] [column subscript]
  Row Subscript and column subscript: int expression
  The range of row subscript is [0, line length-1]
  Column subscript value range is [0, column length-1]

  int a[3][2]; 3 Rows, 2 columns, 6 elements
  A[0][0] a[0][1]
  A[1][0] a[1][1]
  A[2][0] a[2][1]

  2). Initialization of two-D arrays
  

• Initial value of branch assignment
  int A[3][3] = {{1, 2, 3}, {4, 5, 6}, {7, 8, 9}};
  static int B[4][3] = {{1, 2, 3}, {}, {4, 5}};

  Array A
  1 2 3
  4 5 6
  7 8 9

  Array b
  1 2 3
  0 0 0
  4 5 0
  0 0 0

• Sequential assignment of initial values
  int a[3][3] = {1, 2, 3, 4, 5, 6, 7, 8, 9};
  static int B[4][3] = {1, 2, 3, 0, 0, 0, 4, 5};

• When assigning initial values to all elements of an array, the number of rows cannot be omitted, but the number of columns can be omitted
  Omit line length
  The initial value is assigned to all elements.
  int a[][3] = {1, 2, 3, 4, 5, 6, 7, 8, 9};
  Or branch is assigned an initial value, all rows are listed in the initial value table
  static int b[][3] = {{1, 2, 3}, {}, {4, 5}, {}}

  3). Programming with two-dimensional arrays
  <1>. Matrix Transpose
  Enter a positive integer n (1<n≤6), generate 1 N-n square matrices according to the following formula, then transpose the Phalanx (row and column interchange) and output.
  A[I][J] = i n + j + 1 (0≤i≤n-1,0≤j≤n-1)
  Analysis: int a[6][6]; When n=3

  The code is:

  #include <stdio.h>int main(void){   int i, j, n, temp;    int a[6][6];     printf ( "Enter n: “ );   scanf ( "%d", &n );     /* 给二维数组赋值  略…… */   /* 行列互换 */  for ( i = 0; i < n; i++ )        for ( j = 0; j < n; j++ )            if ( i <= j ){             /* 只遍历上三角阵 */        temp = a[i][j]; a[i][j] = a[j][i]; a[j][i] = temp;            }    /* 按矩阵的形式输出a  略…… */    

  
  <2> Calculate date
  

  Code:

  <font size=5 color="black">int year,  month,  day;    int k, leap;    int tab[2][13] = {                          {0, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31},         {0, 31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31}     };    scanf("%d %d %d", &year, &month, &day);    leap = (year % 4 == 0 && year%100!=0 || year%400==0);     for(k = 1; k < month; k++)    {       day = day + tab[leap][k];   }           printf("day = %d\n", day) ;     

  2. One-dimensional character array
  

• The storage and operation of strings can be implemented with a one-dimensional character array
  
The definition, reference, and initialization of one-dimensional character arrays is the same as other types of one-dimensional arrays.
Char str[80];
Defines an array of 80-character elements str
Char t[5]={' H ', ' a ', ' P ', ' P ', ' Y '};
Initializing an array of T

1). String


• Storage of strings-array initialization
  Strings can be stored in a one-dimensional character array
  static char s[6] = {' H ', ' a ', ' P ', ' P ', ' Y ', ' n '};
  Character array initialization: using string constants
  static char s[6] = {"Happy"};
  static char s[6] = "Happy";
  Array length ≥ string valid length + 1
  Char t[5]; Can "Happy" be deposited in T?
  

• Storage of strings

• Operations on strings
  

• Storage of strings-assignment and input
  

• Programming with strings

  Learning process this week
  

15-week job (two-dimensional array)