1. ICOM 4015 Advanced Programming
Lecture 3
Busqueda y Ordenamiento I
Reading: LNN Chapters 9,10 & 16
Prof. Bienvenido Vélez
5/31/2019
ICOM 4015

2. Búsqueda y Ordenamiento
Topic 1
why arrays?
declaration/initialization/acess
array parameters
Topic 2
Searching algorithms
Topic 3
Sorting algorithms
5/31/2019
ICOM 4015

3. Static Arrays I Outline
Why arrays?
Array declaration, initialization and access
Array parameters
Examples of array usage:
statistics on arrays
array reversal
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ICOM 4015

4. Why arrays? Want to represent groups of homogeneous objects BUT
Do not want nor care to give each group member a different name.
Solution:
Access members by position
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ICOM 4015

5. Statistics - main function
// Standard C++ header files
#include <cmath>
#include <iostream>
// Forward declarations of local functions
template <class T> T sqr (T x);
int readData();
void printReport(int N, float max, float min, float avg, float stdev);
// Global definitions
const int ArrayLength = 100;
float numbers[ArrayLength];
// Main function
int main() {
// Read data into numbers array
int counter = readData();
cout << "Read " << counter << " numbers" << endl;
if (counter == 0) return 0;
// Compute Max, Min and Avg in first pass
float maxDatum = numbers[0];
float minDatum = numbers[0];
float sum = 0;
for(int i=0; i<counter; i++) {
sum += numbers[i];
maxDatum = (maxDatum > numbers[i]) ? maxDatum : numbers[i];
minDatum = (minDatum < numbers[i]) ? minDatum : numbers[i]; }
float avg = sum / counter;
// Compute Std deviation in second pass
float sumDevs = 0;
sumDevs += sqr(numbers[i] - avg);
float stdev = sqrt(sumDevs / counter);
// Print report
printReport(counter, maxDatum, minDatum, avg, stdev);
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ICOM 4015
stats.cc

6. Statistics Auxiliary functions
// Auxiliary local functions
int readData() {
int counter = 0;
while(true) {
cout << "Next datum: ";
float nextDatum;
cin >> nextDatum;
if (cin.eof()) break;
numbers[counter++] = nextDatum; }
return counter;
void printReport(int N, float max, float min, float avg, float stdev)
cout << "Report:" << endl;
cout << "N: " << N << endl;
cout << "Max: " << max << endl;
cout << "Min: " << min << endl;
cout << "Avg: " << avg << endl;
cout << "Std Dev: " << stdev << endl;
template <class T> T sqr (T x) { return x * x;};
stats.cc
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ICOM 4015

7. Statistics Output [bvelez@amadeus] ~/icom4015/lec10 >>arrays
Next datum: 3
Next datum: 4
Next datum: 5
Next datum: 6
Next datum: Read 4 numbers
Report: N:
Max: 6
Min: 3
Avg:
Std Dev:
~/icom4015/lec10 >>
5/31/2019
ICOM 4015

8. Anatomy of an Array Definition
array name
ID[0]
ID[1]
ID[2]
ID[3]
ID[4]
ID[dim-1]
type ID [ dim ]
element
type
number of cells
starting from 0
Arrays are zero-offset in C++
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ICOM 4015

9. Array Basics Summary of Concepts
Arrays are compound objects used to represent groups of homogeneous objects
Each cell of an array must have the same type
Array elements are accessed by position (index)
An array of n cells has elements indexed from 0 to n-1
An attempt to access a cell beyond the boundaries of the array (below 0 or above n-1) may yield runtime errors that are difficult to detect and fix. Check your boundaries!
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ICOM 4015

10. Anatomy of an Array Parameter Definition
array name
int f(int a[], int length)
array dimension
unspecified
type of
elements
number of cells
additional
parameter
5/31/2019
ICOM 4015

11. Reversing and array Main function
// Standard C++ header files
#include <cmath>
#include <iostream>
// Forward declarations of local functions
template <class T> swap(T& a, T& b);
template <class T> int readData(istream& source, T data[], int maxlen);
template <class T> void printArray(ostream& sink, T a[], int length);
template <class T> void reverseArray(T a[], int length);
// Main function
int main() {
// Define local array to hold input data
const int ArrayLength = 100;
float numbers[ArrayLength] = { 0.0 }; // Inititalize all cells to 0
// Read data from standard input
int counter = readData(cin, numbers, ArrayLength);
cout << "Read " << counter << " numbers" << endl;
if (counter == 0) return 0;
cout << "Original Array:" << endl;
printArray(cout, numbers, counter);
reverseArray(numbers, counter);
cout << "Reversed Array:" << endl; }
array-params..cc
5/31/2019
ICOM 4015

12. Reversing and Array Auxiliary Functions
// Auxiliary local functions
template <class T>
int readData(istream& source, T data[], int maxlen) {
int counter = 0;
while(counter < maxlen) {
cout << "Next datum: ";
float nextDatum;
source >> nextDatum;
if (source.eof()) break;
data[counter++] = nextDatum; }
return counter;
void printArray(ostream& sink, T a[], int length)
for (int i=0; i<length; i++) {
sink << a[i] << endl;
void reverseArray(T a[], int length)
int iterations = length / 2;
for (int i=0; i<iterations; i++) {
swap(a[i], a[length - i - 1]);
template <class T> swap(T& a, T& b)
{ T temp = a; a = b; b = temp; }
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ICOM 4015
array-params.cc

13. Example 1 Output
~/icom4015/lec11 >>array-params
Next datum: 1
Next datum: 2
Next datum: 3
Next datum: 4
Next datum: 5
Next datum: 6
Next datum: 7
Next datum: 8
Next datum: 9
Next datum: 10
Next datum: Read 10 numbers
Original Array: 1 2 3 4 5 6 7 8 9 10
Reversed Array:
~/icom4015/lec11 >>
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ICOM 4015

14. Array Parameters Summary
Arrays are passed by reference by default
Compiler ignores array dimension in parameter declaration
Programmer typically passes array length as extra parameter. No way to tell array length from array itself.
5/31/2019
ICOM 4015