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Arrays

Arrays. One-Dimensional initialize & display Arrays as Arguments Part I. char, int, float, double. array, struct, union, class. Data Types. simple or atomic structured. * *. Structured Data Type - Array.

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Arrays

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  1. Arrays One-Dimensional initialize & display Arrays as Arguments Part I

  2. char, int, float, double array, struct, union, class Data Types • simple or atomic • structured * *

  3. Structured Data Type - Array • An array is a collection of data storage locations, each of which holds the same type of data. Each storage location is called an element of the array. • An homogeneous aggregate of elements • Each element is referred to as an indexed or subscripted variable.

  4. Array Declaration • Syntax dataType arrayName [ ConstIntExpression ] • The number of elements in an array is • stated within square brackets, [ ]. • Examples double angle [4]; const int POLY = 8; int testScore [12]; double angle [POLY]; char password [8];

  5. Array Storage • Each array has sufficient memory reserved to hold the number of data items of the given type. • Initializing an array sets up the address of the first element. Addresses of all other elements are offsets from the starting address. • Array elements occupy contiguous memory locations.

  6. Array Element Access • Syntax • arrayName [ indexExpression ] • Program access to each of the array elements is by referring to an offset from the array name. Array elements are counted beginning with zero. • A[0] => add zero to the address of A (1st element) • A[3] => add (3 * width of element) to the address of A (4th element)

  7. Array Element Access • double angle[4]; // declaration • Example angle [0] = 6.21; angle [1] = 15.89; angle [2] = 7.5; angle [3] = -45.7; angle sub zero = 6.21angle sub one = 15.89angle sub two = 7.5angle sub three = -45.7 6.21 15.89 7.5 -45.7 angle3 --Mathematical notation * * *

  8. Using Array Elements • write the contents of an array element: cout << angle[2]; // the third element • assign values to an array element: cin >> angle[3]; // the fourth element angle[2] = pow(axis,4); // the third element • use it as a parameter: y = sqrt(angle[0]); // the first element • use it in an expression: x = 2.5 * angle[1] + 64; // the second element * * * *

  9. Declare an Array • float myArray[100]; • Want to reset myArray to zeros • myArray = 0.0; // works in some languages • In C++, the array name is a pointer to an address in memory • myArray is an address in memory An attempt to assign a float to a pointer to a float

  10. Array Component Access Zero out an entire array. (Initialize every element to 0.0.) • for(index=0; index < arraySize; index++) myArray[index] = 0.0; 100 For loops were “made for” arrays You always know how many times the loop will execute – once for each element * *

  11. [ 0 ] [ 1 ] [ 2 ] [ 3] @#$ @#$ Off Set intangle[4]; angle • memoryaddresses • starting address • off set by one unit • off set by two units • off set by three units

  12. [ 0 ] [ 1 ] [ 2 ] [ 3] @#$ @#$ Out-of-Bounds Array Index angle • memoryaddresses • angle[4] = 135;cout << angle[5]; Overwrites value in memory without warning! grade score

  13. Declare an Array • Syntax type arrayName[index]; Example double dailyHigh[31] ; int quizGrade[29] ; char YSUID[9] ; *

  14. Initialize an Array Element • Syntax arrayName[index] = value; Example dailyHigh[18] = 16.7; quizGrade[2] = 15; YSUID[3] = ‘7’; *

  15. Initialize an Array at Declaration Time double angle[4] = {16.21, 15.89, 7.5, -45.7}; double convert[5] = {.64, .89, .76, .83, .65}; int scores[12] = {210, 198, 203, 188, 200, 224, 220, 217, 211, 194, 197, 189}; double iona[8] = {0.0}; // fill with zeros *

  16. int scores[ ] = {210, 198, 203, 188, 200, 224, 220, 217, 211, 194, 197, 189}; Initialize an Array - Variations Space for 12 integers char name1[4] = {‘Z’, ‘o’, ‘l’, ‘a’}; char name2[4] = “Zola”; // no braces or , char phrase [ ] = “Hello World”; 5 Will not compile: “init string too long” Compiler will allocate 12 bytes * *

  17. Character Arrays - \0 char name1[4] = {‘Z’, ‘o’, ‘l’, ‘a’}; char name2[5] = “Zola”; // no braces or , needs 5 slots to have space for the end of string character, \0 char phrase [ ] = “Hello World”; Compiler will allocate 12 bytes * *

  18. Sequencing Through an Array • Use the for statement to sequence through an array. • Assume an array with 7 grades in it… • Total the contents of an array: sum = 0; for (index=0; index < 7; index++) sum += grades[index]; • char name1[4] = {‘Z’, ‘o’, ‘l’, ‘a’}; • Print out an array • for (i = 0, i < 4 , i++) • cout << name1[i]; // prints Zola

  19. Loading an Array – with cin grade 0 75 85 65 95 77 88 68 93 59 90 • double grade[10]; • int index; • for(index=0; index < 10; index++){ cout<<“Enter a grade “; • cin >> grade[index]; • } 9

  20. Finding the Max/Min Value • Set the max or min to element zero. • Use a for loop to cycle through the array. • Compare each element to the max/min. • If necessary, assign a new value to max/min. How would you do this? *

  21. Finding the Maximum Value • double find_max(int temp[30]) • { • int max = temp[0]; //only max seen thus far • for(int index=1; index < 30; index++) if (temp[index] > max)max = temp[index]; • return (max); • } If the current temp[ ] is bigger than the max seen thus far. Remember this one! *

  22. Finding the Minimum Value • double find_min(int temp[30]) • { • int min = temp[0]; // minimum thus far • for(int index = 1; index < 30; index++) if (temp[index] <min)min = temp[index]; • return ( min ); • } *

  23. Aggregate Assignment - NOT! • There are no aggregate assignments with arrays. That is, you may not assign one array to another. • int x[5] = {11, 22, 33, 44, 55}; • int y[5]; • y = x; y[ ] = x[ ]; for (i=0;i<5;i++) y[i] = x[i];

  24. Arrays as Arguments • double find_max(int temp[ ]) • { • max = temp[0]; • for(index = 1; index < 30; index++) if (temp[index] > max) max = temp[index]; • return max; • } double find_max(int temp[ ]) Leave blank or use constant *

  25. Passing an Array or Elements • find_max(temp); // whole array, no [ ] • inventory(price, quantity, amount); // 3 arrays • words(cuplet); Elements of an array • find_max(temp[3]); • inventory(price, quantity[4], amount[12]); • words(cuplet[0]); *

  26. Comparing Arrays as Arguments to Simple Data Types • formal parameter formal parameter declaration for declaration forparameterPass-by-Value Pass-by-Reference • simple var. int cost int& pricearray impossible int myArray[ ] • array const int source[ ] Keeps function from changing values in the array

  27. Passing an Array Element • Follows the rules for the type of an element in the array • int cntA[1111]; • cntA[33] is an int and is treated as any other int when used as an actual argument. • cntA refers to the entire array. • It is the addressof the array or a pointer to the array.

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  30. 1-D Array Review • An array is a structured data type • 1st element is “arrayName subzero” • Array Declaration int myArray [9]; • Array Initialization int myArray [9 ] = { 9, 9, 9, 8, 7, 6, 5, 4, 3}; • Array Element Reference myArray [3]; // value = 8 const int MAXELS = 9; Use everywhere instead of the literal 9 *

  31. optional 1-D Array Review • Arrays are always passed by reference, unless const added to the formal parameter. • Array in a Function Prototype • void myFunction(int [9]); • Array in a Function Call myFunction(myArray); • Array in a Function Header void myFunction(int anyArrayName[9])

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