C Sc 227 Practice 6 Quiz Name ________________________________ 50pts
ANSWERS
1. Complete method numberOf100s that uses recursion to return the number of elements in an
integer array that are equal to 100. No loops needed. These assertions must pass: (12 pts)
public int numberOf100s(int[] x, int n) {
if (n == 0)
return 0;
else if (x[n - 1] == 100)
return 1 + numberOf100s(x, n - 1);
else
return 0 + numberOf100s(x, n - 1); // 0 not necessary
}
-or-
public int numberOf100s(int[] x, int n) {
if (n == 0)
return 0;
else {
int hasOne = 0;
if (x[n - 1] == 100)
hasOne++;
return hasOne + numberOf100s(x, n - 1);
}
}
2. Complete method range that uses recursion to return the range of integers in an array. No
loops needed. You may use a helper method but you may not use instance variables. All
variables must be local. These assertions must pass: (13pts)
public int range(int[] x, int n) {
int maxVal = x[0];
int minVal = x[0];
return range(x, maxVal, minVal, n - 1);
}
private int range(int[] x, int maxVal, int minVal, int rightIndex) {
if (rightIndex < 0)
return maxVal - minVal;
else {
if (x[rightIndex] < minVal)
minVal = x[rightIndex];
if (x[rightIndex] > maxVal)
maxVal = x[rightIndex];
return range(x, maxVal, minVal, rightIndex - 1);
}
}
3. To RecursiveList, add method get that uses recursion to get an element at the given index. No
loops needed. If the index is out of range, return null. These assertions must pass. (12pts)
