關鍵找到每個元素的出現的次數:
方法一:
res=0
for i in set(nums):
res=nums.count(i)*(nums.count(i)-1)/2+res
return res
方法二:
returnsum(v * (v -1) //2 for v in Counter(nums).values())
關鍵找到每個元素的出現的次數:
方法一:
res=0
for i in set(nums):
res=nums.count(i)*(nums.count(i)-1)/2+res
return res
方法二:
returnsum(v * (v -1) //2 for v in Counter(nums).values())