1.two-sum.java

/*
 * @lc app=leetcode id=1 lang=java
 *
 * [1] Two Sum
 */

// @lc code=start
class Solution {
    public int[] twoSum(int[] nums, int target) {
        Map<Integer, Integer> map = new HashMap<>();
        
        for (int i = 0; i < nums.length; i++) {
            int sum = target - nums[i];
            if (map.containsKey(sum)) {
                return new int[]{i, map.get(sum)};
            }
            map.put(nums[i], i);
        }
        return new int[]{};
    }
}
// @lc code=end