Two Sum
Description
Given an array of integers nums and an integer target, return indices of the two numbers such that they add up to target. You may assume that each input would have exactly one solution, and you may not use the same element twice. You can return the answer in any order.
Example 1:
Input: nums = [2, 7, 11, 15], target = 9
Output: [0, 1]
Explanation: nums[0] + nums[1] = 2 + 7 = 9, so we return [0, 1].
Example 2:
Input: nums = [3, 2, 4], target = 6
Output: [1, 2]
Explanation: nums[1] + nums[2] = 2 + 4 = 6, so we return [1, 2].
Example 3:
Input: nums = [3, 3], target = 6
Output: [0, 1]
Explanation: nums[0] + nums[1] = 3 + 3 = 6, so we return [0, 1].
Constraints
2 <= nums.length <= 10^4-10^9 <= nums[i] <= 10^9-10^9 <= target <= 10^9Only one valid answer exists
Complexity
Show Complexity
- Time:
O(n) - Space:
O(n)
Hints
Show Hints
- Pattern
- Hash map for complement lookup
- Approach
- For each number x, check if (target - x) exists in hash map. If yes, return indices. Otherwise, add x to map.
- Complexity
- Use hash map to store seen values and their indices
Solutions
Show PY Solution
def solution(nums, target):
container = {}
for i in range(len(nums)):
if nums[i] in container:
return [container[nums[i]], i]
t = target - nums[i]
container[t] = i
return []