Two Dimensional Arrays

1
Two Dimensional Arrays

• float p210
• 20 floats being associated as 10 pairs.
• p0i can be taken as equivalent to xi
• p1i can be taken as equivalent to yi

2
Weather Balloon

• As a weather balloon is used to measure
  temperature as it rises.
• Measurements are taken at fixed time intervals.
• We need to keep track of the height as well as
  the temperature.

3
Height vs Time
height
time
4
Measure Height Temperature

• float fBalloon210, fSumOfHT0.0
• int i,n
• printf("How many points? ") scanf("d",n)
• for(i0 iltn i)
• printf(height and temperature values at d
  ",i)
• scanf("ff", fBalloon0i,
  fBalloon1i)
• for(i0 iltn i)
• fSumOfHTfSumOfHT
• fBalloon0i fBalloon1i

5
Input

• float fBalloon210, fSumOfHT0.0
• int i,n
• printf("How many points? ")
• scanf("d",n)
• for(i0 iltn i)
• printf(height and temperature
• values at d ",i)
• scanf("ff", fBalloon0i,
  fBalloon1i)

6
Calculation

• for(i0 iltn i)
• fSumOfHTfSumOfHT
• fBalloon0i fBalloon1i

7
Initialization

• include ltstdio.hgt
• void main()
• int i, j, k2500,01,02,03,04,
• 10,11,12,13,14
• float f520.0, 0.1,
• 1.0,1.1,
• 2.0,2.1,
• 3.0,3.1,
• 4.0,4.1
• for(i0 ilt5 i)
• for(j0 jlt2 j)
• printf("fdd is .1f",i, j,
  fij)
• printf(" kdd is 02d\n",j, i,
  kji)

8
Initialization

• include ltstdio.hgt
• void main()
• int i, j, k2500,01,02,03,04,
• 10,11,12,13,14
• float f52 0.0, 0.1,
• 1.0,1.1,
• 2.0,2.1,
• 3.0,3.1,
• 4.0,4.1

9
Output

• for(i0 ilt5 i)
• for(j0 jlt2 j)
• printf("fdd is .1f",i, j,
• fij)
• printf(" kdd is 02d\n",j, i,
• kji)

10
Default Initialization

• include ltstdio.hgt
• void main()
• int i, j, k2599
• for(i0 ilt5 i)
• for(j0 jlt2 j)
• printf(" kdd is 02d\n",j,
• i, kji)

11
Surface

• void main()
• float z2121
• int x, y
• for(x0 xlt21 x)
• for(y0 ylt21 y)
• zxy((x-15)(x15)(y-5)(y-5))

12

13
3D Array

• include ltstdio.hgt
• void main()
• int m432000,001,010,011,020,021
  ,
• 100,101,110,111,120,121
  ,
• 200,201,210,211,220,221
  ,
• 300,301,310,311,320,321
  , i, j, k
• for(i0 ilt4 i)
• for(j0 jlt3 j)
• for(k0 klt2 k)
• printf("d d d value is
  d\n",i,j,k,mijk)

14
Initialization

• include ltstdio.hgt
• void main()
• int m432000,001,010,011,020,021,
• 100,101,110,111,120,121,
• 200,201,210,211,220,221,
• 300,301,310,311,320,321,
• i, j, k

15
Output

• for(i0 ilt4 i)
• for(j0 jlt3 j)
• for(k0 klt2 k)
• printf("d d d value is
• d\n",i,j,k,mijk)

16
Out of Bounds

• What happens if
• int a10
• a1123
• We can get an error that is not easily detected.
• Some systems will check this, Borland on Windows
  does not.

17
Array Passing to Functions

• include ltstdio.hgt
• define SIZE 4
• void PrintArray(int ) //Prototype
• void main()
• int aSIZE0,1,2,3
• PrintArray(a) //Function call
• void PrintArray(int x) //Declaration
• int i
• for(i0 iltSIZE i)
• printf("d d\n",i,xi)

18
main and Prototype

• include ltstdio.hgt
• define SIZE 4
• void PrintArray(int ) //Prototype
• void main()
• int aSIZE0,1,2,3
• PrintArray(a) //Function call

19
Function

• void PrintArray(int x) //Declaration
• int i
• for(i0 iltSIZE i)
• printf("d d\n",i,xi)

20
Variable Number of Elements

• include ltstdio.hgt
• define SIZE 4
• void PrintArray(int , int)
• void main()
• int aSIZE0,1,2,3
• PrintArray(a, 3)
• void PrintArray(int x, int n)
• int i
• for(i0 iltn i)
• printf("d d\n",i,xi)

21
main and Prototype

• include ltstdio.hgt
• define SIZE 4
• void PrintArray(int , int)
• void main()
• int aSIZE0,1,2,3
• PrintArray(a, 3)

22
Function

• void PrintArray(int x, int n)
• int i
• for(i0 iltn i)
• printf("d d\n",i,xi)

23
Passing Multidimensions

• include ltstdio.hgt
• void PrintArray(int 3) //Prototype
• void main()
• int a230,1,2,3,4,5
• PrintArray(a) //Function call
• void PrintArray(int x3) //Declaration
• int i,j
• for(i0 ilt2 i)
• for(j0 jlt3 j)
• printf("d d d\n",i,j,xij)

24
main and Prototype

• include ltstdio.hgt
• void PrintArray(int 3) //Prototype
• void main()
• int a230,1,2,3,4,5
• PrintArray(a) //Function call

25
Function

• void PrintArray(int x3) //Declaration
• int i,j
• for(i0 ilt2 i)
• for(j0 jlt3 j)
• printf("d d d\n",i,j,xij)

26
Notes

• In one dimensional arrays, we do not have to be
  explicit about the number of elements
• void PrintArray(int )
• In multi-dimensional arrays, we do have to be
  explicit about the number of elements in every
  level except the first
• void PrintArray(int 3)
• These define the shape.