Roughly commit

Author: fibers

.gitignore

@@ -5,3 +5,6 @@
 target
 *.class
 *.iml
+.classpath
+.project
+.settings/

src/main/java/com/fibers/algorithm/leetcode/_015/Solution.java

@@ -1,9 +1,53 @@
 package com.fibers.algorithm.leetcode._015;
 
+import com.fibers.utils.Utils;
+
+import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.List;
 
 public class Solution {
+    public static void main(String[] args) {
+        Solution s = new Solution();
+        int[] ar = new int[]{1, -1, -1, 0};
+        Utils.printNestList(s.threeSum(ar));
+    }
+
     public List<List<Integer>> threeSum(int[] nums) {
-        return null;
+
+        List<List<Integer>> results = new ArrayList<>();
+        if (nums == null || nums.length < 3) {
+            return results;
+        }
+
+        Arrays.sort(nums);
+
+        for (int i = 0; i < nums.length - 2; i++) {
+            if (i == 0 || (i > 0 && nums[i] != nums[i - 1])) {
+                int low = i + 1;
+                int high = nums.length - 1;
+                int sum = 0 - nums[i];
+
+                while (low < high) {
+                    if (nums[low] + nums[high] == sum) {
+                        results.add(Arrays.asList(nums[i], nums[low], nums[high]));
+                        while (low < high && nums[low] == nums[low + 1]) {
+                            low++;
+                        }
+                        while (low < high && nums[high] == nums[high - 1]) {
+                            high--;
+                        }
+                        low++;
+                        high--;
+                    } else if (nums[low] + nums[high] < sum) {
+                        low++;
+                    } else {
+                        high--;
+                    }
+                }
+            }
+        }
+
+        return results;
     }
 }