diff --git a/src/main/kotlin/g0801_0900/s0855_exam_room/ExamRoom.kt b/src/main/kotlin/g0801_0900/s0855_exam_room/ExamRoom.kt
index e43d50dd1..4c6fddf1a 100644
--- a/src/main/kotlin/g0801_0900/s0855_exam_room/ExamRoom.kt
+++ b/src/main/kotlin/g0801_0900/s0855_exam_room/ExamRoom.kt
@@ -50,7 +50,7 @@ class ExamRoom() {
         var maxAtLeft: Node? = null
         var cur = tail.pre
         while (cur !== head && cur!!.pre !== head) {
-            val pre = cur!!.pre
+            val pre = cur.pre
             val at = (cur.`val` + pre!!.`val`) / 2
             val distance = at - pre.`val`
             if (distance >= max) {
diff --git a/src/main/kotlin/g1101_1200/s1171_remove_zero_sum_consecutive_nodes_from_linked_list/Solution.kt b/src/main/kotlin/g1101_1200/s1171_remove_zero_sum_consecutive_nodes_from_linked_list/Solution.kt
index 0d4bfdd31..e6583537f 100644
--- a/src/main/kotlin/g1101_1200/s1171_remove_zero_sum_consecutive_nodes_from_linked_list/Solution.kt
+++ b/src/main/kotlin/g1101_1200/s1171_remove_zero_sum_consecutive_nodes_from_linked_list/Solution.kt
@@ -30,7 +30,7 @@ class Solution {
                     curr = curr!!.next
                     key += curr!!.`val`
                 }
-                map.getValue(preSum).next = curr!!.next
+                map.getValue(preSum).next = curr.next
             } else {
                 map[preSum] = curr
             }
diff --git a/src/main/kotlin/g2801_2900/s2815_max_pair_sum_in_an_array/Solution.kt b/src/main/kotlin/g2801_2900/s2815_max_pair_sum_in_an_array/Solution.kt
index dbb974b0a..411e11663 100644
--- a/src/main/kotlin/g2801_2900/s2815_max_pair_sum_in_an_array/Solution.kt
+++ b/src/main/kotlin/g2801_2900/s2815_max_pair_sum_in_an_array/Solution.kt
@@ -3,7 +3,6 @@ package g2801_2900.s2815_max_pair_sum_in_an_array
 // #Easy #Array #Hash_Table #2023_12_06_Time_223_ms_(82.35%)_Space_37.6_MB_(100.00%)
 
 import java.util.PriorityQueue
-import kotlin.collections.HashMap
 import kotlin.math.max
 
 @Suppress("NAME_SHADOWING")