三数之和

Author: haotf

Diff for: 11.盛最多水的容器.java

@@ -0,0 +1,25 @@
+/*
+ * @lc app=leetcode.cn id=11 lang=java
+ *
+ * [11] 盛最多水的容器
+ */
+
+// @lc code=start
+class Solution {
+    public int maxArea(int[] height) {
+        int max = 0;
+        int left = 0;
+        int right = height.length - 1;
+
+        while (left < right) {
+            max = Math.max(max, (right - left) * Math.min(height[left], height[right]));
+            if (height[left] < height[right]) {
+                left++;
+            } else {
+                right--;
+            }
+        }
+        return max;
+    }
+}
+// @lc code=end

Diff for: 15.三数之和.java

@@ -0,0 +1,63 @@
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Comparator;
+import java.util.List;
+
+/*
+ * @lc app=leetcode.cn id=15 lang=java
+ *
+ * [15] 三数之和
+ */
+
+// @lc code=start
+class Solution {
+    public List<List<Integer>> threeSum(int[] nums) {
+        Arrays.sort(nums);
+        return nSum(nums, 0, 3, 0);
+    }
+
+    private List<List<Integer>> nSum(int[] nums, int start, int n, int target) {
+        List<List<Integer>> res = new ArrayList<>();
+        if (nums.length < n || n < 2)
+            return res;
+
+        if (n == 2) {
+            int left = start;
+            int right = nums.length - 1;
+            while (left < right) {
+                int sum = nums[left] + nums[right];
+                int low = nums[left];
+                int high = nums[right];
+                if (sum < target) {
+                    while (nums[left] == low && left < right)
+                        left++;
+                } else if (sum > target) {
+                    while (nums[right] == high && left < right)
+                        right--;
+                } else {
+                    List<Integer> rList = new ArrayList<>();
+                    rList.add(nums[left]);
+                    rList.add(nums[right]);
+                    res.add(rList);
+                    while (nums[left] == low && left < right)
+                        left++;
+                    while (nums[right] == high && left < right)
+                        right--;
+                }
+            }
+        } else {
+            for (int i = start; i < nums.length; i++) {
+                List<List<Integer>> result = nSum(nums, i + 1, n - 1, target - nums[i]);
+
+                for (List<Integer> list : result) {
+                    list.add(0, nums[i]);
+                    res.add(list);
+                }
+                while (i < nums.length - 1 && nums[i] == nums[i + 1])
+                    i++;
+            }
+        }
+        return res;
+    }
+}
+// @lc code=end