448_Find_All_Numbers_Disappeared_in_an_Array

Author: qiyuangong

README.md

@@ -133,6 +133,7 @@ Remember solutions are only solutions to given problems. If you want full study
 | 437 | [Path Sum III](https://leetcode.com/problems/path-sum-iii/) | [Python](https://github.com/qiyuangong/leetcode/blob/master/python/437_Path_Sum_III.py) [Java](https://github.com/qiyuangong/leetcode/blob/master/java/437_Path_Sum_III.java) | 1. Recursively travese the whole tree, O(n^2)<br>2. Cache sum in Hash based on solution 1. Note that if sum(A->B)=target, then sum(root->a)-sum(root-b)=target.|
 | 438 | [Find All Anagrams in a String](https://leetcode.com/problems/find-all-anagrams-in-a-string/) | [Python](https://github.com/qiyuangong/leetcode/blob/master/python/438_Find_All_Anagrams_in_a_String.py) [Java](https://github.com/qiyuangong/leetcode/blob/master/java/438_Find_All_Anagrams_in_a_String.java) | Build a char count list with 26-256 length. Note that this list can be update when going through the string. O(n) and O(1) |
 | 443 | [String Compression](https://leetcode.com/problems/string-compression/description/) | [Python](https://github.com/qiyuangong/leetcode/blob/master/python/443_String_Compression.py) [Java](https://github.com/qiyuangong/leetcode/blob/master/java/443_String_Compression.java) | Maintain curr, read, write and anchor (start of this char). |
+| 448 | [Find All Numbers Disappeared in an Array](https://leetcode.com/problems/find-all-numbers-disappeared-in-an-array/) | [Python](https://github.com/qiyuangong/leetcode/blob/master/python/448_Find_All_Numbers_Disappeared_in_an_Array.py) [Java](https://github.com/qiyuangong/leetcode/blob/master/java/448_Find_All_Numbers_Disappeared_in_an_Array.java) | Value (1, n) and index (0, n-1). Mark every value postion as negative. Then, the remain index with positive values are result. O(n)|
 | 453 | [Number of Segments in a String](https://leetcode.com/problems/minimum-moves-to-equal-array-elements/description/) | [Python](https://github.com/qiyuangong/leetcode/blob/master/python/453_Minimum_Moves_to_Equal_Array_Elements.py) [Java](https://github.com/qiyuangong/leetcode/blob/master/java/453_Minimum_Moves_to_Equal_Array_Elements.java) | Each move is equal to minus one element in array, so the answer is the sum of all elements after minus min. |
 | 461 | [Hamming Distance](https://leetcode.com/problems/hamming-distance/) | [Python](https://github.com/qiyuangong/leetcode/blob/master/python/461_Hamming_Distance.py) [Java](https://github.com/qiyuangong/leetcode/blob/master/java/461_Hamming_Distance.java) | Hamming Distance is related to XOR for numbers. So, XOR then count 1. O(n) |
 | 463 | [Island Perimeter](https://leetcode.com/problems/island-perimeter/) | [Python](https://github.com/qiyuangong/leetcode/blob/master/python/463_Island_Perimeter.py) [Java](https://github.com/qiyuangong/leetcode/blob/master/java/463_Island_Perimeter.java) | math, find the area, actual number, then find the digit |

java/448_Find_All_Numbers_Disappeared_in_an_Array.java

@@ -0,0 +1,20 @@
+class Solution {
+    // https://leetcode.com/problems/find-all-numbers-disappeared-in-an-array/discuss/92956/Java-accepted-simple-solution
+     public List<Integer> findDisappearedNumbers(int[] nums) {
+        List<Integer> ret = new ArrayList<Integer>();
+        
+        for(int i = 0; i < nums.length; i++) {
+            int val = Math.abs(nums[i]) - 1;
+            if(nums[val] > 0) {
+                nums[val] = -nums[val];
+            }
+        }
+        
+        for(int i = 0; i < nums.length; i++) {
+            if(nums[i] > 0) {
+                ret.add(i+1);
+            }
+        }
+        return ret;
+    }
+}

python/448_Find_All_Numbers_Disappeared_in_an_Array.py

@@ -0,0 +1,18 @@
+class Solution(object):
+    def findDisappearedNumbers(self, nums):
+        """
+        :type nums: List[int]
+        :rtype: List[int]
+        """
+        # https://leetcode.com/problems/find-all-numbers-disappeared-in-an-array/discuss/92956/Java-accepted-simple-solution
+        res = []
+        if nums:
+            n = len(nums)
+            for i in range(n):
+                val = abs(nums[i]) - 1
+                if nums[val] > 0:
+                    nums[val] = -nums[val]
+            for i in range(n):
+                if nums[i] > 0:
+                    res.append(i + 1)
+        return res