1. func singleNumber(nums []int) int {
  2.     hm := map[int]int{}
  3.     for _, v := range nums {
  4.         x := hm[v] + 1
  5.         hm[v] = x
  6.     }
  7.     for k, v := range hm {
  8.         if v == 1 {
  9.             return k
  10.         }
  11.     }
  12.     return 0
  13. }

位运算

func singleNumber(nums []int) int {
    single := 0
    for _, num := range nums {
        single ^= num
    }
    return single
}