LeetCode in Kotlin
3694. Distinct Points Reachable After Substring Removal
Medium
You are given a string s consisting of characters 'U', 'D', 'L', and 'R', representing moves on an infinite 2D Cartesian grid.
'U': Move from(x, y)to(x, y + 1).'D': Move from(x, y)to(x, y - 1).'L': Move from(x, y)to(x - 1, y).'R': Move from(x, y)to(x + 1, y).
You are also given a positive integer k.
You must choose and remove exactly one contiguous substring of length k from s. Then, start from coordinate (0, 0) and perform the remaining moves in order.
Return an integer denoting the number of distinct final coordinates reachable.
Example 1:
Input: s = “LUL”, k = 1
Output: 2
Explanation:
After removing a substring of length 1, s can be "UL", "LL" or "LU". Following these moves, the final coordinates will be (-1, 1), (-2, 0) and (-1, 1) respectively. There are two distinct points (-1, 1) and (-2, 0) so the answer is 2.
Example 2:
Input: s = “UDLR”, k = 4
Output: 1
Explanation:
After removing a substring of length 4, s can only be the empty string. The final coordinates will be (0, 0). There is only one distinct point (0, 0) so the answer is 1.
Example 3:
Input: s = “UU”, k = 1
Output: 1
Explanation:
After removing a substring of length 1, s becomes "U", which always ends at (0, 1), so there is only one distinct final coordinate.
Constraints:
1 <= s.length <= 105sconsists of only'U','D','L', and'R'.1 <= k <= s.length
Solution
class Solution {
fun distinctPoints(s: String, k: Int): Int {
val seen: MutableSet<Long> = HashSet()
seen.add(0L)
var x = 0
var y = 0
for (i in k..<s.length) {
// add new step
when (s[i]) {
'U' -> y++
'D' -> y--
'L' -> x++
'R' -> x--
else -> x--
}
// remove old step
when (s[i - k]) {
'U' -> y--
'D' -> y++
'L' -> x--
'R' -> x++
else -> x++
}
seen.add(1000000L * x + y)
}
return seen.size
}
}