992 DataStruAlgo Arrays

7/31/2019 992 DataStruAlgo Arrays

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Data Structures and Algorithms

Data type and Arrays

Instructor: Chien-Yu ChenBIME@NTU


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Chien-Yu Chen, BIME@NTU

Choice of proper data structure

once the choice has been made, the

necessary algorithms are simple.

For the same data, some datastructures require more or less space

than others; for the same operations

on the data, some data structures

lead to more or less efficientalgorithms than others.


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Data structure

A data structure is not a passive object: We

also must consider the operations to be

performed on it (and the algorithms used for

these operations). The data structures that we consider in this

chapter are important building blocks that

we can use in a natural manner in C++ and

many other programming languages.


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type and function

Types allow us to specify how we will

use particular sets of bits and

functions allow us to specify the

operations that we will perform on the

data.


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Basic type of data

Integers (ints)

int, lont int, short int

Floating-point numbers (floats) float, double

Characters (chars)


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Type-dependent operations


7/23Chien-Yu Chen, BIME@NTU

Program 3-1


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Program 3-2


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Program 3-2 (cont.)


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Changing data type


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Using header file

In C++, an alternative approach is to

put the typedef and randNum into a

separate header filecalled, say,

Number.hreplacing them with thedirective

include Number.h

in the code in Program 3.2.


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interface


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An example in C

/* in the file named Number.h */

typedef int Number;

Number randNum();

/* in the file named int.c */

#include #include Number.h

Number randNum()

{ return rand(); }

/* in the file named avg.c */

#include #include

#include Number.h

...


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pointer

Apointeris a reference to an object inmemory (usually implemented as amachine address).

We declare a variable a to be a pointer to

(for example) an integer by writing int *a,and we can refer to the integer itself as *a.

We can declare pointers to any type ofdata. The unary operator& gives the

machine address of an object, and is usefulfor initializing pointers. For example, *&a is the same as a.


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New data type

Implementation

Using it


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Arrays

a[i]


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Using pointers


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Sieve of Eratosthenes

Eratosthenes (276~194 BC) .Eratosthenes (Sieve). , 100

2~100 2, 2 , 2

3, 3 , 3

5, 5 , 5

..., , ,

2,3,5,7,...,97 100

http://home.educities.edu.tw/kuen/maths/algorithm01.htm


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Dynamic memory allocation


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992 DataStruAlgo Arrays

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