LeetCode in Kotlin
279. Perfect Squares
Medium
Given an integer n, return the least number of perfect square numbers that sum to n.
A perfect square is an integer that is the square of an integer; in other words, it is the product of some integer with itself. For example, 1, 4, 9, and 16 are perfect squares while 3 and 11 are not.
Example 1:
Input: n = 12
Output: 3
Explanation: 12 = 4 + 4 + 4.
Example 2:
Input: n = 13
Output: 2
Explanation: 13 = 4 + 9.
Constraints:
1 <= n <= 104
Solution
@Suppress("NAME_SHADOWING")
class Solution {
private fun validSquare(n: Int): Boolean {
val root = Math.sqrt(n.toDouble()).toInt()
return root * root == n
}
fun numSquares(n: Int): Int {
var n = n
if (n < 4) {
return n
}
if (validSquare(n)) {
return 1
}
while (n and 3 == 0) {
n = n shr 2
}
if (n and 7 == 7) {
return 4
}
val x = Math.sqrt(n.toDouble()).toInt()
for (i in 1..x) {
if (validSquare(n - i * i)) {
return 2
}
}
return 3
}
}