Introduction to algorithms and data structures in C

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Introduction to algorithms and data structures in
C

• jesus.ibanez_at_upf.edu

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Introduction

• Jesús Ibáñez Martínez

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Introduction

• Philosophy learn to program by programming
• Bibliography

The C Programming Language, Second Edition by
Brian W. Kernighan and Dennis M. Ritchie.
Prentice Hall. http//cm.bell-labs.com/cm/cs/cbo
ok/index.html
Programació I web page by Toni Navarrete
http//www.tecn.upf.es/tnavarrete/programacio1/
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von Neumann architecture
CPU
Input
Output
Memory
Instructions Data
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Program design
Problem
Program

• Program Design Process has 2 phases
• Problem Solving Phase
• Creates an algorithm that solves the problem
• Implementation (Coding) Phase
• Translates the algorithm into a programming
  language

Algorithm
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Levels
CAB
High-Level Languages
LOAD A ADD B STORE C
Assembly Languages
1300042774 1400593419 1200274027
Machine Languages
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Compiler vs interpreter

• Compiler
• Interpreter
• Hybrid solution virtual machine

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Programming paradigms

• Main paradigms
• Imperative. It uses a programming process that
  follows a sequence of commands, that when
  executed manipulate data to produce a solution.
• Examples Machine languages, Basic, C, Pascal,
  Cobol, Fortran, Algol
• Declarative. Based on logical deduction, and
  require the programmer to develop an accurate and
  precise statement of the problem rather than
  discovering an algorithm for solving it.
• Examples PROLOG, GPSS.

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Programming paradigms

• Main paradigms
• Functional. We express computation as the
  evaluation of mathematical functions. These are
  nested inside the language like black boxes,
  which accept input and produce output
• Examples LISP, MIL, Scheme, C
• Object Oriented. Units of data are viewed as
  active objects, instead of being merely a passive
  collection of data controlled by a program.
• Examples C, JAVA, SIMULA, SMALLTALK,ada95,
  Visual Basic
• C is imperative and functional

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C language

• History
• 1972, Dennis Ritchie, Bell Laboratories at ATT,
  created to develop UNIX
• 1983, ANSI C
• First program
• include ltstdio.hgt
•  
• main()
• printf(Hello world!")

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Compilation
C library
hello.o
compile
a.out a.exe
hello.c
Link
Edit
Source File
Object File
Executable
gcc hello.c
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Summary

• A program is like a recipe. It contains a list of
  ingredients (called variables) and a list of
  directions (called statements) that tell the
  computer what to do with the variables. The
  variables can represent numeric data, text, or
  graphical images.

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Summary

• Variables and constants
• Basic data types
• Numbers
• Characters
• Booleans
• Expressions

• Statements
• Assignments
• Input and output
• Control of flow
• Sequential
• Conditional
• Iterative

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Variables

• A variable is a named memory location
• The contents of a variable can change
• All variables in C must be declared before use.
• data_type var1, var2,
• Where data_type is one of the four basic types
  (integer, character, float, or double) and varx
  are identifiers.

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Variables

• include ltstdio.hgt
•  
• main()
• int x
• x3
• printf(The value of the variable x is d", x)

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Constants

• include ltstdio.hgt
•  
• main()
• const float pi3.1416
• printf(The value of the constant pi is f",
  pi)
•  
•  

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Constants

• include ltstdio.hgt
• define pi 3.1416
•  
• main()
• printf(The value of the constant pi is f",
  pi)

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Identifiers

• Identifiers is C must begin with a character or
  underscore, and may be followed by any
  combination of characters, underscores, or the
  digits 0-9
• summary exit_flag i12 _id
• You should ensure that you use meaningful (but
  short) names for your identifiers
• distance speed time
• Do not use reserved identifiers
• if, else, while,

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Basic data types

• Data types
• Numbers
• Integers (int)
• Fractional (float, double)
• Characters (char)
• Boolean
• Modifiers short, long, unsigned

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Numbers

• include ltstdio.hgt
•  
• main()
• const float pi3.1416
• float radi
• float area
•  
• printf(Enter the radius ")
• scanf("f",radi)
•  
• area pi radi radi
•  
• printf(The surface is f",area)

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Characters

• include ltstdio.hgt
•  
• main()
• char c,d
• c 'A'
• d c
• a ! A
• C treats character as integers. The ASCII code is
  used to associate each character with an integer.

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Characters

• a ! A
• C treats character as integers. The ASCII code is
  used to associate each character with an integer.
• A \101 \x41
• Special characters
• \b backspace
• \n newline
• \t tab
• \
• \
• \\ \

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Characters

• Special characters
• \b backspace
• \n newline
• \t tab
• \
• \
• \\ \
• printf(Hello \bworld)
• printf(Hello\bworld)
• printf(Hello \nworld)
• printf(Hello \tworld)

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Boolean

• 0 gt FALSE
• Other integer value gt TRUE

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Expressions

• An expression in C is some combination of
  constants, variables, operators and function
  calls.
• a (b c)
• Operators
• Arithmetic operators
• Logic operators
• Relational operators

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Arithmetic operators
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Logic operators
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Relational operators
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Boolean logic
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Statements

• A statement in C is an expression terminated with
  a semicolon.
• Assignment operator
• a 5 3
• b a
• Increment/Decrement operators
• i is equivalent to i i 1
• i is equivalent to i i 1
• --i is equivalent to i i 1
• i-- is equivalent to i i 1

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Decision making statements
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Decision making statements (if)
if(expression) statement

• include ltstdio.hgt
• main()
• int number
•   printf( Enter an integer ")
• scanf("d",number)
• if (number lt0)
• number number (-1)
• printf(Its absolute value is d", number)

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Decision making statements (if-else)
if(expression) statement1 else statement2

• if the expression is TRUE, statement1 is
  executed statement2 is skipped
• if the expression is FALSE, statement2 is
  executed, statement1 is skipped

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Decision making statements (if-else)

• include ltstdio.hgt
• main()
• float nota1,nota2,nota3,notafinal
• printf("Introdueix la primera nota ")
• scanf("f",nota1)
• printf("Introdueix la segona nota ")
• scanf("f",nota2)
• printf("Introdueix la tercera nota ")
• scanf("f",nota3)
• notafinal (nota1nota2nota3)/3
• if (notafinalgt5)
• printf("La nota final es APROVAT")
• else
• printf("La nota final es SUSPENS")

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Decision making statements (if-else)

• main()
• int n1,n2
•  
• printf("Enter the first integer ")
• scanf("d",n1)
• printf("Enter the second integer ")
• scanf("d",n2)
•  
• if (n1gtn2)
• printf(The greater is d",n1)
• else
• printf(The greater is d",n2)

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Decision making statements (if-else)

• include ltstdio.hgt
•  
• main()
• int lloc
• printf("Introdueix el lloc on ha acabat
  l'esportista ")
• scanf("d",lloc)
• if (lloc1)
• printf("Medalla d'or")
• else
• if (lloc2)
• printf("Medalla d'argent")
• else

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Decision making statements (if-else)

• if (lloc3)
• printf("Medalla de bronze")
• else
• if ((llocgt3) (lloclt9))
• printf("Diploma olimpic")
• else
• printf("Cap premi")

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Decision making statements (switch)

switch (expression) case constant1 statem
ent1 break case constant2 statement2
break ... default statement
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Decision making statements (switch)

• include ltstdio.hgt
• main()
• int lloc
• printf("Introdueix el lloc on ha acabat
  l'esportista ")
• scanf("d",lloc)
• switch (lloc)
• case 1
• printf("Medalla d'or")
• break
• case 2
• printf("Medalla d'argent")
• break
• case 3
• printf("Medalla de bronze")
• break

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Decision making statements (switch)

• case 4
• case 5
• case 6
• case 7
• case 8
• printf("Diploma olimpic")
• break
• default
• printf("Cap premi")
• break