leetcode LargestDivisibleSubset
z
 2019-04-09 10:36:27   
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import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class LargestDivisibleSubset {
  /**
   * 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]
   */
  public List<Integer> largestDivisibleSubset(int[] nums) {

    int n = nums.length;
    int dp[] = new int[n];
    int ptr[] = new int[n];

    for (int i=0; i<ptr.length; i++){
      ptr[i] = -1;
    }

    List<Integer> res = new ArrayList<>();

    int idx=0;
    Arrays.sort(nums);

    for (int i=1; i<nums.length; i++){
      for (int j=0; j<i; j++){
        if (nums[i] % nums[j]==0){
          dp[i] = dp[j] + 1;
          ptr[i] = j;
          if (dp[i] > dp[idx]){
            idx = i;
          }
        }
      }
    }

    while(idx != -1){
      res.add(nums[idx]);
      idx = ptr[idx];
    }
    return res;
  }
}