Lec05Arrays_6per.pdf

# Lec05Arrays_6per.pdf - EECS 402 Further Updates To Sum...

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1 The University Of Michigan Andrew M. Morgan EECS402 Lecture 05 Savitch Ch. 5 Arrays Multi-Dimensional Arrays EECS EECS 402 EECS 402 Andrew M Morgan 2 Consider This Program int i0, i1, i2; int sum; cout << "Enter int #1: "; cin >> i0; cout << "Enter int #2: "; cin >> i1; cout << "Enter int #3: "; cin >> i2; cout.setf(ios::right); cout << " " << setw(4) << i0 << endl; cout << "+ " << setw(4) << i1 << endl; cout << "+ " << setw(4) << i2 << endl; cout << " ----" << endl; sum = i0 + i1 + i2; cout << " " << setw(4) << sum << endl; Write a program to input 3 ints and output each value and their sum, formatted like a math problem Enter int #1: 54 Enter int #2: 102 Enter int #3: 7 54 + 102 + 7 ---- 163 EECS EECS EECS EECS 402 EECS 402 Andrew M Morgan 3 Update To Program #1 Your boss was so impressed, you are asked to update the program to work with 5 ints instead of 3 int i0, i1, i2, i3, i4; int sum; cout << "Enter int #1: "; cin >> i0; cout << "Enter int #2: "; cin >> i1; cout << "Enter int #3: "; cin >> i2; cout << "Enter int #4: "; cin >> i3; cout << "Enter int #5: "; cin >> i4; cout.setf(ios::right); cout << " " << setw(4) << i0 << endl; cout << "+ " << setw(4) << i1 << endl; cout << "+ " << setw(4) << i2 << endl; cout << "+ " << setw(4) << i3 << endl; cout << "+ " << setw(4) << i4 << endl; cout << " ----" << endl; sum = i0 + i1 + i2 + i3 + i4; cout << " " << setw(4) << sum << endl; Enter int #1: 50 Enter int #2: 30 Enter int #3: 108 Enter int #4: 1215 Enter int #5: 74 50 + 30 + 108 + 1215 + 74 ---- 1477 EECS 402 402 EECS 402 Andrew M Morgan 4 Further Updates To Sum Program The previous programs worked fine and solved the problem that was presented Changing from 3 to 5 ints was easy – lots of copy/paste operations Now you boss asks for a program that works on 100 ints Do you copy/paste 95 more inputs and outputs, update the variable names, and hope you did everything correctly? What if you are then requested to write one for 87 ints, and then 1000 ints, and then 743 ints, etc? EECS 402 EECS 402 Andrew M Morgan 5 Intro To Arrays Array: A list of variables, all of the same data type that can be accessed via a common name The length of an array (the number of elements in the list) can be of any fixed length Syntax for declaring an array: dataType arrayName[arrayLength]; dataType: Any available data type (int, float, user-defined types, etc) arrayName: The name of the array (i.e. the common name used to access any variable in the list) arrayLength: The number of elements that can be accessed via this array Example: int quizGrades[10]; Declares an array of 10 integer elements, with the name "quizGrades" EECS EECS 402 EECS 402 Andrew M Morgan 6 More Info On Arrays Individual elements of the array are accessed by "indexing" To index into an array, use the square brackets In C/C++ array indices start at 0, and end at (length – 1) Example: quizGrades[4] accesses the fifth element of the array [0] would be the first, [1] the second, [2] the third, [3] the fourth, etc. "quizGrades" is an array, but "quizGrades[4]" is an int, and can be used anywhere an int variable can be used If an int variable requires 4 bytes of memory, then the declaration: int quizGrades[10]; sets aside 40 bytes (10 ints at 4 bytes each) of memory Elements can be accessed using the following: quizGrades[0], quizGrades[1], quizGrades[2], quizGrades[3], quizGrades[4],

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