An aerospace engineer is writing an algorithm to sort drone altitudes in ascending order using a bubble sort.
Figure 1 shows the engineer's draft algorithm:
1 altitudes[0] ← 120
2 altitudes[1] ← 85
3 altitudes[2] ← 210
4 altitudes[3] ← 145
5 altitudes[4] ← 95
6 FOR p ← 0 TO 3
7 FOR q ← 0 TO 3
8 IF altitudes[q + 1] < altitudes[q] THEN
9 hold ← altitudes[q]
10 altitudes[q] ← altitudes[q + 1]
11 altitudes[q + 1] ← hold
12 ENDIF
13 ENDFOR
14 ENDFOR
In a previous draft of this algorithm, lines 6 and 7 were written as:
6 FOR p ← 0 TO 4
7 FOR q ← 0 TO 4
Explain why the algorithm would result in a runtime error if the value 4 was used instead of 3 on line 7.