Given an array of integers nums and an integer target, return the indices of the two numbers that add up to target.
You may assume that each input would have exactly one solution, and you may not use the same element twice.
Example 1
Input: nums = [2,7,11,15], target = 9
Output: [0,1]
Explanation: nums[0] + nums[1] == 9
Example 2
Input: nums = [3,2,4], target = 6
Output: [1,2]
Explanation: nums[1] + nums[2] == 6
2 <= nums.length <= 10^4-10^9 <= nums[i] <= 10^9Only one valid answer exists.Try a hash map to store each number and its index as you iterate.
public int[] twoSum(int[] nums, int target) {
Map<Integer, Integer> seen = new HashMap<>();
for (int i = 0; i < nums.length; i++) {
int complement = target - nums[i];
if (seen.containsKey(complement)) {
return new int[]{seen.get(complement), i};
}
seen.put(nums[i], i);
}
throw new IllegalArgumentException("No solution");
}Time: O(n) · Space: O(n)