Largest Divisible Subset

Author: ishpreet-singh

Diff for: 13.cpp

@@ -0,0 +1,44 @@
+/*
+
+Largest Divisible Subset
+------------------------
+
+Given a set of distinct positive integers, find the largest subset such that every pair (Si, Sj) of elements in this subset satisfies:
+
+Si % Sj = 0 or Sj % Si = 0.
+
+If there are multiple solutions, return any subset is fine.
+
+Example 1:
+
+Input: [1,2,3]
+Output: [1,2] (of course, [1,3] will also be ok)
+Example 2:
+
+Input: [1,2,4,8]
+Output: [1,2,4,8]
+*/
+
+class Solution {
+public:
+    vector<int> largestDivisibleSubset(vector<int>& nums) {
+        int n = nums.size();
+        sort(nums.begin(), nums.end());
+
+        vector<int> v, next(n, -1), count(n, -1);
+        int x = -1;
+        for (int i = 0; i < n; ++i) {
+            for (int j = 0; j < i; ++j) {
+                if (nums[i] % nums[j] != 0) continue;
+                if (next[i] == -1 || count[j] > count[next[i]]) next[i] = j;
+            }
+            count[i] = (next[i] == -1) ? 1 : count[next[i]]+1;
+            if (x == -1 || count[i] > count[x]) x = i;
+        }
+
+        while (x != -1) { v.push_back(nums[x]); x = next[x]; }
+        reverse(v.begin(), v.end());
+
+        return v;
+    }
+};

Diff for: README.md

@@ -13,4 +13,5 @@
 |   9  |         Is Subsequence         |  [Link](https://github.com/ishpreet-singh/leetcode-june-challenge/blob/master/9.cpp) |
 |  10  |     Search Insert Position     | [Link](https://github.com/ishpreet-singh/leetcode-june-challenge/blob/master/10.cpp) |
 |  11  |           Sort Colors          | [Link](https://github.com/ishpreet-singh/leetcode-june-challenge/blob/master/11.cpp) |
-|  12  |  Insert Delete GetRandom O(1)  | [Link](https://github.com/ishpreet-singh/leetcode-june-challenge/blob/master/12.cpp) |
+|  12  |  Insert Delete GetRandom O(1)  | [Link](https://github.com/ishpreet-singh/leetcode-june-challenge/blob/master/12.cpp) |
+|  13  |    Largest Divisible Subset    | [Link](https://github.com/ishpreet-singh/leetcode-june-challenge/blob/master/13.cpp) |