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| 1 | +package algorithm_sites.leetcode; |
| 2 | + |
| 3 | +import java.util.*; |
| 4 | + |
| 5 | +public class LC_00001_TowSum { |
| 6 | + |
| 7 | + public int[] twoSum_1(int[] nums, int target) { |
| 8 | + if (nums.length == 2) { |
| 9 | + return new int[] {0,1}; |
| 10 | + } |
| 11 | + |
| 12 | + for (int i = 0; i < nums.length-1; ++i) { |
| 13 | + for (int j = i+1; j < nums.length; ++j) { |
| 14 | + if (nums[i] + nums[j] == target) { |
| 15 | + return new int[] {i, j}; |
| 16 | + } |
| 17 | + } |
| 18 | + } |
| 19 | + |
| 20 | + return null; |
| 21 | + } |
| 22 | + |
| 23 | + public int[] twoSum_2(int[] nums, int target) { |
| 24 | + if (nums.length == 2) { |
| 25 | + return new int[] {0,1}; |
| 26 | + } |
| 27 | + |
| 28 | + Map<Integer, Integer> map = new HashMap<>(); |
| 29 | + for (int i = 0; i < nums.length; ++i) { |
| 30 | + map.put(nums[i], i); |
| 31 | + } |
| 32 | + |
| 33 | + for (int i = 0; i < nums.length; ++i) { |
| 34 | + if (map.containsKey(target-nums[i])) { |
| 35 | + if (map.get(target-nums[i]) != i) { |
| 36 | + return new int[] {map.get(target-nums[i]), i}; |
| 37 | + } |
| 38 | + } |
| 39 | + } |
| 40 | + |
| 41 | + return null; |
| 42 | + } |
| 43 | + |
| 44 | + public int[] twoSum_3(int[] nums, int target) { |
| 45 | + if (nums.length == 2) { |
| 46 | + return new int[] {0,1}; |
| 47 | + } |
| 48 | + |
| 49 | + Map<Integer, Integer> map = new HashMap<>(); |
| 50 | + for (int i = 0; i < nums.length; ++i) { |
| 51 | + if (map.containsKey(target-nums[i])) { |
| 52 | + return new int[] {map.get(target-nums[i]), i}; |
| 53 | + } |
| 54 | + map.put(nums[i], i); |
| 55 | + } |
| 56 | + |
| 57 | + return null; |
| 58 | + } |
| 59 | + |
| 60 | + public static void main(String args[]) { |
| 61 | + LC_00001_TowSum lc = new LC_00001_TowSum(); |
| 62 | + |
| 63 | + int[] result = lc.twoSum_3(new int[]{3, 2, 4}, 6); |
| 64 | + |
| 65 | + for (int i = 0; i < result.length; ++i) { |
| 66 | + System.out.print(result[i] + " "); |
| 67 | + } |
| 68 | + } |
| 69 | + |
| 70 | +} |
| 71 | + |
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