JavaScriptMediumHashing20 min
Find two indices with a target sum
Return indices [i,j] with i < j whose values sum to target, or [] if none exist. Choose the smallest possible j, then the smallest i. All input is valid JSON satisfying the constraints; do not mutate the meaning of values through type coercion. Interviewers use this problem to assess look up each needed complement in a Map.
Input
A JSON object {"array": [...], "target": integer}.
Output
Print one compact JSON value: two zero-based indices or [].
Constraints
0 <= array length <= 10000; values and target between -1000000 and 1000000.
Example
Input
{"array":[2,7,11,15],"target":9}Output
[0,1]
Example 2 input
{"array":[1,1,2],"target":3}Output
[0,2]
Boundary case: Scan j in increasing order to enforce the tie rule
Public test cases (2)
Input
{"array":[2,7,11,15],"target":9}Expected output
[0,1]
Input
{"array":[3,3],"target":6}Expected output
[0,1]
Hints (2)
- Store only the first index for each value
- Scan j in increasing order to enforce the tie rule
Target complexity: time O(n) · space O(n)