Sum of Two Elements
Easy
Given an array of integers and a target integer, determine if there are two distinct indices i and j in the array such that array[i] + array[j] == target. Return true if such indices exist, otherwise return false.
Example 1
Input
[ [ 10, 15, 3, 7 ], 17 ]
Output
true
Explanation. 10 and 7 sum to 17, which is the target.
Example 2
Input
[ [ 4, 5, 1, 2 ], 8 ]
Output
false
Explanation. No two elements sum to 8.
Example 3
Input
[ [ 5, -2, 4, 9, 1 ], 7 ]
Output
true
Explanation. -2 and 9 sum to 7, which is the target.
Example 4
Input
[ [], 5 ]
Output
false
Explanation. The array is empty; no elements to sum.
Example 5
Input
[ [ 3, 3 ], 6 ]
Output
true
Explanation. The element at index 0 and index 1 sum to target 6.
Follow-up: Can you implement a solution that is better than O(n^2) time complexity using additional data structure?
Constraints:
1. The number of elements in the input array will be at least 2.\n2. The elements of the array and the target are all integers.
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