What are the values of a and b after?

Answer: a=9, b=5 The temp variable preserves a's value while it is overwritten by b.

Answer: 31 3+1+4+1+5+9+2+6 = 31.

Answer: 12 Condition i < a.length - 1 stops at i=2, so a[3]=8 is skipped. Sum is 2+4+6 = 12.

AP Computer Science A · Topic 6.4

Developing Algorithms Using Arrays Practice

Part of Array.

Practice questions

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Sample questions

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Sample 1difficulty 1/5
```
int a = 5, b = 9;
int temp = a;
a = b;
b = temp;
```
$What are the values of a and b after?$
- A
  $a=9, b=5$
  check_circle
- B
  $a=5, b=9$
- C
  $a=5, b=5$
- D
  $a=9, b=9$
Why
$The temp variable preserves a's value while it is overwritten by b.$
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Sample 2difficulty 1/5
```
int[] a = {3, 1, 4, 1, 5, 9, 2, 6};
int sum = 0;
for (int x : a) sum += x;
```
$What is sum?$
- A
  $29$
- B
  $32$
- C
  $30$
- D
  $31$
  check_circle
Why
$3+1+4+1+5+9+2+6 = 31.$
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Sample 3difficulty 2/5
```
int[] a = {2, 4, 6, 8};
int sum = 0;
for (int i = 0; i < a.length - 1; i++) {
  sum += a[i];
}
System.out.println(sum);
```
$What is printed?$
- A
  $12$
  check_circle
- B
  $20$
- C
  $18$
- D
  $8$
Why
$Condition i < a.length - 1 stops at i=2, so a[3]=8 is skipped. Sum is 2+4+6 = 12.$
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Sample 4difficulty 2/5
```
int[] a = {3, 1, 4, 1, 5, 9, 2, 6};
int sum = 0;
for (int i = 2; i < 5; i++) sum += a[i];
```
$What is sum?$
- A
  $9$
- B
  $8$
- C
  $10$
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- D
  $11$
Why
$a[2]+a[3]+a[4] = 4+1+5 = 10.$
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Sample 5difficulty 2/5
```
public static double avg(int[] a) {
    int total = 0;
    for (int x : a) total += x;
    return /* missing */;
}
```
$Which expression computes the average correctly?$
- A
  $a.length / total$
- B
  $total / (double) a$
- C
  $(double) total / a.length$
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- D
  $total / a.length$
Why
$Casting total to double forces floating-point division; otherwise integer division would truncate.$
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