將字串 s 分段，同一字母只能在一段中出現。Partition the string into as many parts as possible so that each letter appears in at most one part.

依照 1 bits 出現的次數排序。

檢查這個 linked list 是否內含迴圈。Given head, the head of a linked list, determine if the linked list has a cycle in it.

檢查陣列中是否有出現重複的值。Return if any value appears at least twice in the array.

將兩兩相鄰的 node 交換順序。Swap every two adjacent nodes.

找出一個陣列中連續整數相加的最大值。Find the contiguous subarray which has the largest sum.