INFSCI 0015 Data Structures Lecture 15: 2dimensional Arrays

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INFSCI 0015 - Data StructuresLecture 15
2-dimensional Arrays

• Peter Brusilovsky
• http//www2.sis.pitt.edu/peterb/0015-011/

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Outline

• 2-dimensional Arrays
• Example Naval Battle
• Example Day of the Month
• Arrays of pointers
• Example Text Reversing

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Two-Dimensional Arrays

• Two-dimensional array is simply a table where
  each cell has two addresses - row and column.
• The way to address an element of a 2-dimensional
  array a is arowcolumn
• Rows and Columns are numbered from 0

a00
a01
a02
a04
a10
a11
a44
a40
int a55
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Declaration and Access

• Declaration with no initialization
• int battlefield1010
• Declaration with initialization
• int battlefield55
• 1, 0, 1, 0, 0,
• 0, 0, 0, 0, 1,
• 0, 0, 1, 0, 0,
• 0, 0, 0, 0, 0,
• 1, 0, 0, 0, 1,
• Access
• battlefield44 1

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Example 15.1 Naval Battle (1)

• include ltstdio.hgt
• define FSIZE 5
• define SHIP 1
• define EMPTY 0
• define DESTROYED 2
• static int battlefieldFSIZEFSIZE
• 1, 0, 1, 0, 0, / row A /
• 0, 0, 0, 0, 1, / row B /
• 0, 0, 1, 0, 0, / row C /
• 0, 0, 0, 0, 0, / row D /
• 1, 0, 0, 0, 1, / row E /

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Example 15.1 Naval Battle (2)

• main()
• int col
• char ch_row
• printf("Enter your move like 5 A\n")
• printf("Enter 0 X to exit\n")
• / reads and process hits /
• do
• printf("You move ")
• scanf("d c\n", col, ch_row)
• while(react(ch_row, col) gt 0)
• return 0

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Example 15.1 Naval Battle (3)

• int react(char r, int col)
• int row
• if (col 0)
• printf("Good Bye!\n") return 0
• row r - 'A'
• if(row lt 0 row gt 4)
• printf("Row c is not possible!\n", r)
• else if (col lt1 col gt5)
• printf("Column d is not possible!\n", col)
• else if (battlefieldrowcol-1 SHIP)
• printf("Hit!\n")
• battlefieldrowcol-1 DESTROYED
• else if (battlefieldrowcol-1
  DESTROYED)
• printf("This ship has been already
  destroyed!\n")
• else printf("Misss...\n")
• return 1

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Example 15.2 Day of the Year
101 of 2000?
Jan
Feb
Dec
Mar
31
31
31
29
101 - 31 70
31
31
31
29
70 - 29 41
31
31
31
29
41 - 31 10
31
31
31
29
101 April 10, 2000
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Example 15.2 Day of the Year

• static char daytab213
• 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,
• void month_day(int year, int yearday, int
  pmonth, int pday)
• int i, leap / 1 for leap year, 0 for non-leap
  /
• leap ((year4 0) year100 ! 0)
  year400 0
• for(i 1 yearday gt daytableapi i)
• yearday - daytableapi
• pmonth i
• pday yearday

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Example 15.2 Day of the Year

• main()
• int year, yday / input data /
• int month, mday / output data /
• do
• printf("Enter Year and Day (yyyy dd) ")
• scanf("d d", year, yday)
• if(yday gt 0)
• month_day(year, yday, month, mday)
• printf("Day d of d is simply d/d/d\n",
• yday, year, month, mday, year)
• else
• printf("Good Bye!\n")
• while(yday gt 0)
• return 0

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Arrays of Pointers
a
b
r
a
\0
c
a
d
a
b
r
\0
c
o
u
r
s
e
\0
strings
c
o
u
r
s
e
s
\0
char strings4 / array of four pointers /
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Memory Allocation malloc
p1 malloc(6)
112300
112301
112302
112303
112304
112305
112306
p1
112307
112308
112309
112310
p2
112311
112312
112313
112314
112300
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Memory Allocation malloc
p2 malloc(8)
112300
112301
112302
112303
112304
112305
112306
p1
112307
112308
112309
112310
p2
112311
112312
112313
112314
112300
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Example 15.3 Reverse Text

• static char lineptrMAXLINES
• main()
• int nlines / counter of input lines read /
• nlines readlines()
• printbackwards(nlines)
• void printbackwards(int n)
• while(n gt 0)
• printf("s", lineptrn-1)
• --n

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Example 15.3 Reverse Text

• define MAXLEN 1000
• int readlines()
• int len, nlines
• char p, line MAXLEN
• nlines 0
• while((len getline(line, MAXLEN)) gt 0)
• p (char ) malloc(len1)
• copy(p, line)
• lineptrnlines p
• nlines
• return nlines

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Initialization of Pointer Arrays

• static char strings4
• "abc", "def", "gh"
• static char picture3
• " ",
• " ",
• "X"

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Example 15.4 More Battle

• static char picture3 " ", " ", "X"
• void printfield(char header)
• int i, j
• / print header /
• printf("s\n\n ", header)
• for(j 0 j lt FSIZE j)
• printf(" d ", j1)
• printf("\n")
• / print field /
• for(i 0 i lt FSIZE i)
• printf("c ", i 'A')
• for(j 0 j lt FSIZE j)
• printf("s ", picture battlefieldij )
• printf("\n")
• printf("\n")

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Two-Dimensional Arrays Again

• Two-dimensional array is really an array of
  one-dimensional arrays
• We can address a whole one-dimensional array as
  arow
• A continuous segment of memory is allocated for a
  2-dimensional array

a0
a00
a01
a02
a04
a10
a11
a1
a44
a40
a4