Two-Pointers-1 solution

MaxArea.java

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+//Time Complexity : O(n)
+//Space Complexity : O(1)
+
+public class MaxArea {
+    public int maxArea(int[] height) {
+        int left = 0;
+        int right = height.length - 1;
+        int max = 0;
+
+        while (left < right) {
+            int area = (right - left) * Math.min(height[left], height[right]);
+            max = Math.max(max, area);
+
+            if(height[left] < height[right]) left++;
+            else right--;
+        }
+
+        return max;
+    }
+}

SortColors.java

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+//Time Complexity : O(n)
+//Space Complexity : O(1)
+
+public class SortColors {
+    public void sortColors(int[] nums) {
+
+        int low = 0;
+        int mid = 0;
+        int high = nums.length - 1;
+
+        while(mid<=high) {
+            if(nums[mid] == 0) {
+                swap(nums, mid, low);
+                mid++;
+                low++;
+            }
+            else if (nums[mid] == 2){
+                swap(nums, mid, high);
+                high--;
+            } else {
+                mid++;
+            }
+        }
+
+    }
+
+    private void swap(int[] nums, int a, int b) {
+        int temp = nums[a];
+        nums[a] = nums[b];
+        nums[b] = temp;
+    }
+}

ThreeSum.java

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+//Time Complexity : O(n^2)
+//Space Complexity : O(1)
+
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+
+public class ThreeSum {
+
+    public List<List<Integer>> threeSum(int[] nums) {
+        Arrays.sort(nums);
+        List<List<Integer>> result = new ArrayList<>();
+        for(int i = 0; i < nums.length ; i++) {
+            if(nums[i] > 0) break;
+            if(i > 0 && nums[i-1] == nums[i]) {
+                continue;
+            }
+
+            int left = i+1;
+            int right = nums.length - 1;
+
+            while (left < right) {
+                int curr = nums[left] + nums[right] + nums[i];
+                if (curr == 0) {
+                    List<Integer> li = new ArrayList<>(List.of(nums[i],nums[left],nums[right]));
+                    result.add(li);
+                    left++;
+                    right--;
+                    while(left< right && nums[left] == nums[left-1]) {
+                        left++;
+                    }
+                    while(left< right && nums[right] == nums[right+1]) {
+                        right--;
+                    }
+                }
+                else if(curr > 0) {
+                    right--;
+                } else {
+                    left++;
+                }
+            }
+        }
+        return result;
+    }
+
+}