Given an array of integers, return indices of the two numbers such that they add up to a specific target.
You may assume that each input would have exactly one solution, and you may not use the same element twice.
Example:
Given nums = [2, 7, 11, 15], target = 9,
Because nums[0] + nums[1] = 2 + 7 = 9,
return [0, 1].
Solution：Hashmap
Time Complexity: O(N) Space Complexity: O(N)
Solution Code：
class Solution {
public int[] twoSum(int[] nums, int target) {
int result[] = new int[2];
HashMap<Integer, Integer> map = new HashMap<Integer, Integer>();
for(int i = 0; i < nums.length; i++) {
if(map.containsKey(target - nums[i])) {
result[0] = map.get(target - nums[i]);
result[1] = i;
return result;
}
map.put(nums[i], i);
}
return result;
}
}
