Prbl1TwoSum.java

//Given an array of integers nums and an integer target, return indices of the t
//wo numbers such that they add up to target. 
//
// You may assume that each input would have exactly one solution, and you may n
//ot 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]
//Output: Because nums[0] + nums[1] == 9, we return [0, 1].
// 
//
// Example 2: 
//
// 
//Input: nums = [3,2,4], target = 6
//Output: [1,2]
// 
//
// Example 3: 
//
// 
//Input: nums = [3,3], target = 6
//Output: [0,1]
// 
//
// 
// Constraints: 
//
// 
// 2 <= nums.length <= 105 
// -109 <= nums[i] <= 109 
// -109 <= target <= 109 
// Only one valid answer exists. 
// 
// Related Topics Array Hash Table 
// 👍 17601 👎 629

package leetcode.editor.en;

import java.util.HashMap;
import java.util.Map;

//java: Two Sum
public class Prbl1TwoSum {
    public static void main(String[] args) {
        Solution solution = new Prbl1TwoSum().new Solution();
        solution.twoSum((new int[]{2, 7, 11, 15}), 9);
    }

    //leetcode submit region begin(Prohibit modification and deletion)
    class Solution {
        public int[] twoSum(int[] nums, int target) {
            int pos1 = 0, pos2 = 0;
            Map<Integer, Integer> hashMap = new HashMap<>(2 << 7);
            for (int i = 0; i < nums.length; i++) {
                hashMap.put(nums[i], i);
            }
            for (int i = 0; i < nums.length; i++) {
                int need = target - nums[i];
                if (hashMap.containsKey(need) && hashMap.get(need) != i) {
                    pos1 = i;
                    pos2 = hashMap.get(need);
                }
            }
            return new int[]{pos1, pos2};
        }
    }
//leetcode submit region end(Prohibit modification and deletion)

}