Module 7 – Part I - PowerPoint Presentation

Module 7 – Part I 1D Arrays and Lots of Brackets 11/2/2019 CSE 1321 Module 7 1

Creating and Initializing Arrays 11/2/2019 CSE 1321 2

Array Creation Example 1) Create an empty array. By default, 0s are stored in the array. int myArray [5];2) Creates and initializes in one line. The stored values are show in { }; int myArray [] = {10, 20, 30, 40, 50}; 11/2/2019 CSE 1321 3

3. Accessing InformationCopy information out of a particular slot Example: CREATE clientAge // IntegerclientAge ← myArray[4]This copies information from the fifth slot (slot four) into the variable clientAge11/2/2019 CSE 1321 4

Horrible, but works…// creates empty array with 5 slots, 0-4 CREATE myArray [5] //Assigns literal values to each index in the array.myArray [0] ← 10myArray[1] ← 20myArray[2] ← 30myArray[3] ← 40myArray [4] ← 50 11/2/2019 CSE 1321 5 Ps

Accessing and Modifyingint main() {int myArray[]={7,4,5,3,2,1,8};//Accessingint secondNumber = myArray[1]; cout <<secondNumber <<endl;//ModifyingmyArray[3] = 42; cout<<myArray[3]<<endl ;}11/2/2019 CSE 1321 Module 46

Traversing the ArrayYou will use a loop to visit every cell of the array Problem: create an array of 5 bytes and fill each slot with the number 42Solution: CREATE myArray [5] FOR i ← 0 to 4 myArray[i] ← 42END FOR 11/2/2019CSE 1321 7 Ps

Traversing an ArrayUse a FOR, WHILE or DO-WHILE starting at index 0 and going thru .length-1 11/2/2019 CSE 1321 8 int main() { int myArray[]={ 7 , 4 , 5 , 3 , 2 , 1 , 8 }; for ( int i = 0;i<7;i++){cout <<myArray[i]<<endl;}}

Another TraceCREATE smallestSoFarsmallestSoFar ← randomArray[0]FOR counter ← 1 to 4 IF (smallestSoFar > randomArray[counter]) THEN smallestSoFar ← randomArray[counter] END IFEND FOR// Done 0 1 2 3 4 42 17 42 -8 4 -8 smallestSoFar 5 counter Ps

Finding the Minimum using a Method (Example1) int FindMin (int* A, int size ) { int temp = A[0]; for (int i=1;i< size;i++){if (temp > A[ i]) { temp = A[i];}} return temp;} int main() { int myArray[]={7,4,5,3,2,1,8,10}; int size= sizeof(myArray)/sizeof (int);cout <<FindMin( myArray,size )<< endl ; } 11/2/2019 CSE 1321 10

11/2/2019CSE 1321 Module 4 11 Finding the Minimum using a Method (Example2) int FindMin ( int* A ) {   int temp = A[0]; for (int i=1;i< *A;i++){   if (temp > A[i])   { temp = A[i];}  }   return temp;}

Finding the sum or average using a method METHOD FINDAVERAGE ( parameter: nums[]) BEGIN sum ← 0 FOR i ← 0 to nums.length - 1 // MOST IMPORTANT LINE IS HERE sum = sum + nums[i] ENDFOR average = sum / nums.length return average END FINDAVERAGE 11/2/2019 12 CSE 1321 Ps

Finding a sum and or average using a method (Example 1)float FindAverage (int* B,int size) {int sum = 0;   for (int i = 0; i < size; i++) {    sum += B[i];   }return (float)sum / size; } int main() {int myArray[]={7,4,5,3,2,1,8,10,11};int size= sizeof(myArray)/ sizeof(int);cout<< FindAverage(myArray,size ); } 11/2/2019CSE 1321 13

Finding a sum and or average using a method (Example 2)float FindAverage (int* B) { int sum=0;   for (int i = 0; i < *B; i++)   {    sum += B[i];   }return sum/ *B; } 11/2/2019 CSE 1321 14

Defining a 2D arrayCREATE array nums [numRows][numColumns] 11/2/2019 CSE 1321 15 Ps

C++ Define a multi-dimension ArrayTwo dimensional array:int two_d[10][20];Three dimensional array: int three_d[10][20][30]; 11/2/2019 CSE 1321 16

Working with 2D arrays Usually involves nested loops, as shown below. Problem Statement: Create an array of 4 rows and 5 columns. Populate the array with the numbers 1-20. ---------------------------------------------------------------------Create array grid[4][5] count ← 1FOR each element in a row FOR each element in a column    grid[row][col] = count count ← count + 1 END INNER FOREND FOR 11/2/2019 CSE 1321 17

11/2/2019 CSE 1321 18 Working with 2D arrays #include <iostream> using namespace std; int main() { int count = 1; //declare a 2D array with 4 rows and 5 columns int grid [4][5]; //getting the rows in the array for (int row = 0; row < 4; row++) { //populate the values in the array (row) we're currently on from the outer loop for (int column = 0; column < 5; column++){ grid[row][column] = count; count++;}}

11/2/2019CSE 1321 Module 4 19 //for each array in the grid (represented by rows)for(auto& rows: grid){//for each element in the array (row) we're currently on from the outer loop for (auto& elem: rows) {cout <<elem <<","; if (elem % 5 == 0){ cout<<" "<<endl; }}}} Working with 2D arrays (Continue……)

Working with Array Lists#include <iostream> //print and take input#include <string> //use string variables #include <list> // for list operations #include <vector> //use vectors#include <algorithm> #include <iterator> //create iterationusing namespace std; 11/2/2019 CSE 1321 20

11/2/2019CSE 1321 Module 4 21 CONTINUED FROM PREVIOUS SLIDEint main() { list<string> colors; // declaring list // initializing array colors.assign(1,"purple"); colors.push_back("pink"); colors.push_back ("green"); cout<<"Does the arraylist contain the color pink?"<<endl;bool found = (find(colors.begin(), colors.end(), "pink") != colors.end());if (found){cout<<"Yes"<<endl;cout<<"\n";} else { cout<<"No"<<endl;cout<<"\n"; }// Printing the assigned list cout << "The list after inserting multiple elements is : "<<endl ; for (list<string>::iterator i=colors.begin(); i!=colors.end(); i ++) cout << * i << " "; cout << endl ;

Working with Array Lists CONTINUED FROM PREVIOUS SLIDE colors.remove("green"); // Printing the assigned list cout << "The list after inserting multiple elements is : "<< endl; for (list<string>::iterator i=colors.begin (); i!=colors.end(); i++) cout << *i << " “<<endl; // Create iterator pointing to first element list<string>::iterator it = colors.begin(); // Advance the iterator by 1 positions, advance(it, 0); // Now iterator it points to 1st element cout << "1st element = " << *it << endl ;} 11/2/2019 CSE 1321 22

11/2/2019CSE 1321 Module 4 23 Using vector:#include <vector> #include <iostream> #include < numeric> using namespace std; int main() { vector<float> v; float input; cout << " Please enter numbers you want to find the mean of:" <<endl; while ( cin >> input) { v.push_back (input); } float average = accumulate( v.begin (), v.end (), 0.0 )/ v.size (); cout << "The average is" << average << endl; return 0; }

11/2/2019CSE 1321 Module 4 24 References :https://stackoverflow.com/questions/28574346/find-average-of-input-to-vector-c