Arrays: Left Rotation Code Challenge Solved
Marcos Rezende
Posted on September 5, 2020
A left rotation operation on an array shifts each of the array's elements 1 unit to the left. For example, if 2 left rotations are performed on array [1, 2, 3, 4, 5], then the array would become [3, 4, 5, 1, 2].
Given an array a of n integers and a number d, perform d left rotations on the array. Return the updated array to be printed as a single line of space-separated integers.
Function Description
Complete the function rotLeft in the editor below. It should return the resulting array of integers.
rotLeft has the following parameter(s):
- An array of integers a
- An integer d, the number of rotations.
Input Format
The first line contains two space-separated integers n and d, the size of a and the number of left rotations you must perform.
The second line contains n space-separated integers a[i].
Constraints
1 <= n <= 10^5
1 <= d <= n
1 <= a[i] <= 10^6
Output Format
Print a single line of n space-separated integers denoting the final state of the array after performing d left rotations.
Sample Input
4
1 2 3 4 5
Sample Output
5 1 2 3 4
Explanation
When we perform left rotations, the array undergoes the following sequence of changes:
[1, 2, 3, 4, 5]
[2, 3, 4, 5, 1]
[3, 4, 5, 1, 2]
[4, 5, 1, 2, 3]
[5, 1, 2, 3, 4]
Solution
function rotLeft($a, $d) {
$i = 0;
$m = $d;
if ($d > sizeof($a)) {
$m = ($d % sizeof($a));
}
while ($i < $m) {
$a[] = $a[$i];
$i++;
}
array_splice($a, 0, $m);
return implode(' ', $a);
}
Posted on September 5, 2020
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