11 1. multi-dimensional array eng

11 1. multi-dimensional array eng

• 1.
  Multidimensional Arrays
• 2.
  2 Two-Dimensional Arrays  Two-DimensionalArray Syntax data_type variable_name[ number][ number ]; Array dimensions Declarations of arrays Remarks int a[100]; a one-demensional array int b[2][7]; a two-demensional array int c[5][3][2]; a three-demensional array
• 3.
  3 Two-Dimensional Arrays  Logicalplacement of int a[3][4] a[0][0] a[0][1] a[0][2] a[0][3] a[1][0] a[1][1] a[1][2] a[1][3] a[2][0] a[2][1] a[2][2] a[2][3] row 0 row 1 col 0 col 1 col 2 col 3 row 2
• 4.
  4 Two-Dimensional Arrays  Two-DemensionalArrays #include <stdio.h> #define M 3 /* number of rows */ #define N 4 /* number of columns */ int main(void){ int a[M][N], i, j, sum = 0; for ( i = 0; i < M; ++i ) for ( j = 0; j < N; ++j ) a[i][j] = i + j; for ( i = 0; i < M; ++i ) { for ( j = 0; j < N; ++j ) printf(“a[%d][%d] = %d “, i, j, a[i][j] ); printf(“n”); } } a[0][0] = 0 a[0][1] = 1 a[0][2] = 2 a[0][3] = 3 a[1][0] = 1 a[1][1] = 2 a[1][2] = 3 a[1][3] = 4 a[2][0] = 2 a[2][1] = 3 a[2][2] = 4 a[2][3] = 5
• 5.
  5 Two-Dimensional Arrays  PhysicalPlacement of int a[3][4] – Two-Dimensional Array is actually stored as the format of 1-Dimensional Array in the computer memory. a[0][0] a[0][1] a[0][2] a[0][3] a[1][0] a[1][1] a[1][2] a[1][3] a[2][0] a[2][1] a[2][2] a[2][3] row 0 row 1 row 2 1000 1016 1032
• 6.
  6 Two-Dimensional Arrays [Ex] int a[2][3],*p ; p = &a[0][0]; p + 0  &a[0][0]  a[0] + 0 p + 1  &a[0][1]  a[0] + 1 p + 2  &a[0][2]  a[0] + 2 p + 3  &a[1][0]  a[0] + 3  a[1] + 0 p + 4  &a[1][1]  a[0] + 4  a[1] + 1 p + 5  &a[1][2]  a[0] + 5  a[1] + 2 a[0][0] a[0][1] a[0][2] a[1][0] a[1][1] a[1][2]
• 7.
  Two-Dimensional Arrays  Physicalplacement of int a[3][4] – If int a[3][4] begins at address 1000, What’s the next value? 7 a = ? a + 1 = ? a[0] = ? a[0] + 1 = ? a[1] = ? a[1] + 1 = ? a[0][0] a[0][1] a[0][2] a[0][3] a[1][0] a[1][1] a[1][2] a[1][3] a[2][0] a[2][1] a[2][2] a[2][3] a[0] a[1] a[2] 1000 1016 1032
• 8.
  8 Two-Dimensional Arrays  Physicalplacement of int a[3][4] – a is a constant, type is int (*)[4] – a[0], a[1], a[2] are each constant, type is int* a[0][0] a[0][1] a[0][2] a[0][3] a[1][0] a[1][1] a[1][2] a[1][3] a[2][0] a[2][1] a[2][2] a[2][3] a[0] a[1] a[2] 1000 1016 1032 &a[0][0] ==a[0]==(int*)1000 &a[1][0]==a[1]==(int*)1016 &a[2][0]==a[2]==(int*)1032 a==&a[0]=(int**)1000 (a+1)==&a[1]=(int**)1016 (a+2)==&a[2]=(int**)1032
• 9.
  9 Two-Dimensional Arrays  Manyways to access the element of Two- Dimensional array – a[ i ] : a element in i th line of array a – a[ i ][ j ] : a element in i th line and j th row of array a – Array name a is equal to &a[0] Expressions equivalent to a[ i ][ j ] *( a[ i ] + j ) ( *( a + i ) ) [ j ] *( ( *( a + i ) ) + j ) *( &a[0][0] + 4 * i + j ) int a[3][4]
• 10.
  10 Two-Dimensional Arrays #include <stdio.h> voidmain() { int a[3][4], j, k, sum = 0 ; for( j = 0 ; j < 3 ; j++ ) for( k = 0 ; k < 4 ; k++ ) scanf( “%d”, &a[j][k] ) ; for( j = 0 ; j < 3 ; j++ ) for( k = 0 ; k < 4 ; k++ ) sum += a[j][k] ; printf( “%dn”, sum ) ; }  Passing Two-Dimensional Array to function #include <stdio.h> int sum(?????) { ... } void main() { int a[3][4], j, k, sum = 0 ; for( j = 0 ; j < 3 ; j++ ) for( k = 0 ; k < 4 ; k++ ) scanf( “%d”, &a[j][k] ) ; printf( “%dn”, sum(????) ) ; }
• 11.
  11 Two-Dimensional Arrays  PassingTwo-Dimensional Array to function int sum( int num[][4], int size ) { for( j = 0 ; j < size ; j++ ) for( k = 0 ; k < 4 ; k++ ) sum += num[j][k] ; } printf( “%dn”, sum(a, 3) ) ; int (*num)[4]
• 12.
   Passing Two-DimensionalArray to function – Why not this? Two-Dimensional Arrays 12 int sum( int num[][], int size0, int size1 ) { for( j = 0 ; j < size0 ; j++ ) for( k = 0 ; k < size1 ; k++ ) sum += num[j][k] ; } printf( “%dn”, sum(a, 3, 4) ) ; If you wrote ‘ int num[3][4] ‘, C compiler converts from num[i][j] to *(base_address + 4*i + j). Thus, If don’t specify 2nd size(4) Then can not convert from num[i][j] to *(base_address + 4*i + j).
• 13.
  Two-Dimensional Arrays  PassingTwo-Dimensional Array to function – Type conversion from 2-Dimensional array to 1-Dimensional array 13 int sum( int num[], int size0, int size1 ) { for( j = 0 ; j < size0 ; j++ ) for( k = 0 ; k < size1 ; k++ ) sum += *(num+ size1*j + k) ; } printf( “%dn”, sum( (int*)a, 3, 4) ) ;
• 14.
  14 Multidimensional Arrays  PassingThree-Dimensional Array to function int sum( int num[][4][5], int size ) { for( j = 0 ; j < size ; j++ ) for( k = 0 ; k < 4 ; k++ ) for( l = 0 ; l < 5 ; l++ ) sum += num[j][k][l] ; } printf( “%dn”, sum(a, 3) ) ; int (*num)[4][5]
• 15.
  Multidimensional Arrays  PassingThree-Dimensional Array to function – Converting to the pointer of 1-dimensional array 15 int sum( int num[], int s0, int s1, int s2 ) { for( j = 0 ; j < s0 ; j++ ) for( k = 0 ; k < s1 ; k++ ) for( l = 0 ; l < s2 ; l++ ) sum += *(num+ s1*s2*j + s2*k + l) ; } printf( “%dn”, sum((int*)a, 3, 4, 5) ) ;
• 16.
  16 Multidimensional Arrays  Initializationof Multi-dimensional Array [Ex] int a[ 2 ][ 2 ][ 3 ] = { { {1,1,0}, {2,0,0} }, { {3,0,0}, {4,4,0} } }; [Ex] int a[ 2 ][ 2 ][ 3 ] = { 0 }; All element are initialized with 0 [Ex] int a[ ][ 2 ][ 3 ] = { { {1, 1}, {2} }, { {3}, {4, 4} } }; [Ex] int a[ 2 ][ 2 ][ 3 ] = { 1, 1, 0, 2, 0, 0, 3, 0, 0, 4, 4, 0 } ;