solve 448.find-all-numbers-disappeared-in-an-array

Author: andavid

vscode/448.find-all-numbers-disappeared-in-an-array.java

@@ -0,0 +1,53 @@
+/*
+ * @lc app=leetcode id=448 lang=java
+ *
+ * [448] Find All Numbers Disappeared in an Array
+ *
+ * https://leetcode.com/problems/find-all-numbers-disappeared-in-an-array/description/
+ *
+ * algorithms
+ * Easy (54.04%)
+ * Likes:    1842
+ * Dislikes: 170
+ * Total Accepted:    174.7K
+ * Total Submissions: 322.9K
+ * Testcase Example:  '[4,3,2,7,8,2,3,1]'
+ *
+ * Given an array of integers where 1 ≤ a[i] ≤ n (n = size of array), some
+ * elements appear twice and others appear once.
+ *
+ * Find all the elements of [1, n] inclusive that do not appear in this array.
+ *
+ * Could you do it without extra space and in O(n) runtime? You may assume the
+ * returned list does not count as extra space.
+ *
+ * Example:
+ *
+ * Input:
+ * [4,3,2,7,8,2,3,1]
+ *
+ * Output:
+ * [5,6]
+ *
+ *
+ */
+class Solution {
+  public List<Integer> findDisappearedNumbers(int[] nums) {
+    List<Integer> list = new ArrayList<>();
+    for (int i = 0; i < nums.length; i++) {
+      int index = Math.abs(nums[i]) - 1;
+      if (nums[index] > 0) {
+        nums[index] = -nums[index];
+      }
+    }
+
+    for (int i = 0; i < nums.length; i++) {
+      if (nums[i] > 0) {
+        list.add(i + 1);
+      }
+    }
+
+    return list;
+  }
+}
+