Problem 5 - C# Programming: From Problem Analysis to Program Design

Question

What value is returned by the method named result? int result(int[ ] anArray, int num) { int i, r; for (r = 0, i = 1; i < num; ++i) if (anArray[i] > anArray [r] ) r = i; return (r); } a. the index of the largest of the first num elements of array anArray b. the value of the largest of the first num elements of array anArray c. the index of the smallest of the first num elements of array anArray d. the value of the smallest of the first num elements of array anArray e. the index of the last element greater than its predecessor within the first num elements of array anArray

Step-by-Step Solution

Answer

a. the index of the largest of the first num elements of array anArray

Step 1: Analyzing the Loop Initialization

The method initializes two variables: a counter variable \( r \) is set to 0, and an iteration variable \( i \) is set to 1. This indicates that the loop will start comparing from the second element of the array \( anArray \) since \( i = 1 \).

Step 2: Explaining the Loop Condition

The loop continues as long as \( i < num \). This means the iterations will continue until the index \( i \) reaches the value of \( num - 1 \). The loop is designed to examine the first \( num \) elements of the array.

Step 3: Understanding the If Statement

Inside the loop, there is a condition \( anArray[i] > anArray[r] \). This checks whether the current element \( anArray[i] \) is greater than the element at index \( r \). If true, \( r \) is updated to the current index \( i \). This means \( r \) will hold the index of the largest value found so far.

Step 4: Determining the Return Value

After the loop finishes, the method returns \( r \). Since \( r \) is updated each time a larger element is found, by the end of the loop, \( r \) holds the index of the largest value among the first \( num \) elements of the array.

Key Concepts

Loop Initialization

In C#, loop initialization is a critical step where we define the variables that will control the loop's execution.
For the provided method, two variables are initialized:

• r is set to 0, which serves as a placeholder for the index of the largest element found so far. Starting with 0 assumes the first element is the largest until proven otherwise.
• i is set to 1, indicating that the first comparison starts with the second element of the array.

It’s important to understand that initializing i with 1 deliberately skips the first element since we compare subsequent elements to it.
Proper loop initialization is vital to ensure the loop functions correctly and doesn’t miss any elements.

Array Indexing

Array indexing in C# is a way to access specific elements within an array using an index value.
In this method, the loop iterates through indices of the array using the variable i.

• Arrays in C# are zero-indexed, meaning the first element is accessed using index 0.
• By initializing i to 1, we start comparing from the second element, while the first element is accessed using anArray[0].

The line inside the loop if (anArray[i] > anArray[r]) utilizes array indexing to compare the current element anArray[i] with anArray[r]. The value of r is updated whenever a larger element is found.
Understanding array indexing is essential for navigating through data structures like arrays effectively.

Conditionals in C#

Conditionals are crucial for decision-making in programming and C# provides versatile tools for such operations.
Within the method, we encounter a conditional statement that influences the variable r:

• if (anArray[i] > anArray[r]): This conditional checks whether the current element is greater than what currently holds the largest position. If true, r is assigned the value of i. This update implies the loop found a new largest element.

Conditionals enable the method to dynamically keep track of the largest number's index. With each iteration, it reevaluates if the current number is greater.
Such logic ensures that by the end of the loop, r accurately reflects the index of the largest element found.

Method Analysis

Analyzing how a method operates involves understanding its logic and purpose step-by-step.
This specific method aims to find the index of the largest element within a specified range in an array.

• The loop initialized with i = 1 and r = 0 iterates through the first num elements of the array.
• During each iteration, the if condition updates r if a larger element is found, ensuring r holds the index of the largest value by loop's end.
• The method ultimately returns r, signifying the conclusion of identifying the largest value's position within the specified array segment.

Through this logical sequencing, the method efficiently determines the desired result, focusing on both correctness and efficiency in execution.