python编程---example14

寻找列表中满足两数之和等于目标值的元素的下标。

def sum_of_two(arr,target):
	dic = {}
	for i,x in enumerate(arr):
		j = dic.get(target-x,-1)
		if j != -1:
 			return((j,i))
 		else:
 			dic[x] = i
 	return([])
 
arr = [2,7,4,9]
target = 6
print(sum_of_two(arr,target))