Chapter 10 MultiDimensional Numeric Arrays

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Chapter 10 Multi-Dimensional Numeric Arrays
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Multidimensional Arrays

• Visual image of matrix or table for
  two-dimensional array
• Subscript for each dimension
• Declared with value for each dimension
  int b2 3

Number of elements 23 6
Lesson 10.1
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Initializing

• Initialized by row
• Example int b2 3 51, 52, 53, 54, 55, 56
• Elements would beb0 0 51 b0 1
  52 b0 2 53b1 0 54 b1 1
  55 b1 2 56

Remember subscripts begin at zero!
Lesson 10.1
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Initializing

• Can use braces to separate rows

int c 4 3 1, 2, 3,
4, 5, 6, 7,
8, 9, 10, 11, 12
Advantage is visual table!
Lesson 10.1
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Initializing
int c4 3 1,2,
4, 5, 6, 7,
10,11,12
If values left outof row, implicitly
initialized to zero. c2 2 0
Lesson 10.1
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Printing
for (j 0 j lt 2 j) for
(k 0 k lt 3 k)
cout ltlt bj k
cout ltlt endl

• Usually use nested for loop
• Two dimensions, two loops
• First loop controls rows
• Second loop controls columns

Lesson 10.1
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Reading Array From File
infile gtgt num_rows gtgt num_cols for (j 0 j lt
num_rows j) for (k 0 k lt
num_cols k)
infile gtgt aj k
Lesson 10.2
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Storage of Two-Dimensional Arrays

• Fills row by row
• If have fewer elements, then storage to the right
  of those filled un-initialized elements
• Three and greater dimensions
• Far right subscript increments first
• Other subscripts increment in order from right to
  left

Lesson 10.2
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Storage
If file gave number of rows as 3 and number of
columns as 4 then have non-contiguous storage.
array5 9


1 2 3 4 2 4 6 8 3 5 7 9

Lesson 10.2
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Storage Location

• Formula to locate arrays element's position in
  memory

sequence location x (J K) y (K) z 1
sequence location 0 (3 4) 1 (4) 21
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Lesson 10.2
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Passing Array to Function
Declaration
void funcName (type, type, type max_cols)
Call
funcName (rows, cols, arrayName)
void funcName (type r, type c, type array
max_cols)
Header
Lesson 10.2
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const Qualifier

• Place in front of array name in function
  declaration and header
• Assures that array is not modified in function

void funcName (type, type, const type col
)
Declaration
Lesson 10.2
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Summary
Learned how to

• Initialize multidimensional arrays
• Print multidimensional arrays
• Read a file for array element values
• Visualize storage
• Pass an array to a function