力扣好數對數目和enumerate用法

1.雜湊表

def

numidenticalpairs
(self, nums: list[
int])-
>
int:
sum=
0 m =[0
]*101for i in nums:
m[i]+=1
for i in m:
if i >1:
sum+=
(i *
(i -1)
)>>
1return
sum

(2)思路：用map表計數遍歷的資料出現的次數，對遍歷值大於1的進行排列組合（ci 2)

2.暴力兩層迴圈

def

numidenticalpairs
(self, nums: list[
int])-
>
int:
count =
0for i in
range(0
,len
(nums)-1
):for j in
range
(i+1
,len
(nums)):
if nums[i]
== nums[j]
: count = count +
1return count

遍歷物件為: 字串、 列表 等

返回值是下標，預設從0開始，和對於列表

clist =[1

,2,3
,4]for i, j in
enumerate
(clist)
:print
(i, j)

011

2233
4

clist =[1

,2,3
,4]for i, j in
enumerate
(clist,1)
:print
(i, j)

112

2334
4

return

sum(
[nums[inx+1:
].count(i)
for inx, i in
enumerate
(nums)
])