The Power of C# List Class

-
The solution to this problem demonstrates the power of the C# List Class. Here it is: https://leetcode.com/problems/queries-on-a-permutation-with-key/

1409. Queries on a Permutation With Key
Medium
Given the array queries of positive integers between 1 and m, you have to process all queries[i] (from i=0 to i=queries.length-1) according to the following rules:
  • In the beginning, you have the permutation P=[1,2,3,...,m].
  • For the current i, find the position of queries[i] in the permutation P (indexing from 0) and then move this at the beginning of the permutation P. Notice that the position of queries[i] in P is the result for queries[i].
Return an array containing the result for the given queries.

Example 1:
Input: queries = [3,1,2,1], m = 5
Output: [2,1,2,1] 
Explanation: The queries are processed as follow: 
For i=0: queries[i]=3, P=[1,2,3,4,5], position of 3 in P is 2, then we move 3 to the beginning of P resulting in P=[3,1,2,4,5]. 
For i=1: queries[i]=1, P=[3,1,2,4,5], position of 1 in P is 1, then we move 1 to the beginning of P resulting in P=[1,3,2,4,5]. 
For i=2: queries[i]=2, P=[1,3,2,4,5], position of 2 in P is 2, then we move 2 to the beginning of P resulting in P=[2,1,3,4,5]. 
For i=3: queries[i]=1, P=[2,1,3,4,5], position of 1 in P is 1, then we move 1 to the beginning of P resulting in P=[1,2,3,4,5]. 
Therefore, the array containing the result is [2,1,2,1].
Example 2:
Input: queries = [4,1,2,2], m = 4
Output: [3,1,2,0]
Example 3:
Input: queries = [7,5,5,8,3], m = 8
Output: [6,5,0,7,5]

Constraints:
  • 1 <= m <= 10^3
  • 1 <= queries.length <= m
  • 1 <= queries[i] <= m
Accepted
7,507
Submissions
9,107

As with many programming languages today, C# also provides a powerful List Class implementation which provides all the different methods needed to tackle this problem, methods such as: insert at any position, delete at any position, find the index of a given element. In few lines one can come up with a very fast running code. Source is below, cheers, and Happy Easter! ACC.


public class Solution
{
    public int[] ProcessQueries(int[] queries, int m)
    {
        List<int> list = new List<int>();

         for (int i = 1; i <= m; i++) list.Add(i);

         int[] retVal = new int[queries.Length];
        for (int i = 0; i < queries.Length; i++)
        {
            int index = list.IndexOf(queries[i]);
            retVal[i] = index;
            list.RemoveAt(index);
            list.Insert(0, queries[i]);
        }

         return retVal;
    }
}

Comments

Post a Comment

Popular posts from this blog

Count Binary Substrings

-
Image
Problem by Leetcode:  https://leetcode.com/problems/count-binary-substrings/description/ Give a string  s , count the number of non-empty (contiguous) substrings that have the same number of 0's and 1's, and all the 0's and all the 1's in these substrings are grouped consecutively. Substrings that occur multiple times are counted the number of times they occur. Example 1: Input: "00110011" Output: 6 Explanation: There are 6 substrings that have equal number of consecutive 1's and 0's: "0011", "01", "1100", "10", "0011", and "01". Notice that some of these substrings repeat and are counted the number of times they occur. Also, "00110011" is not a valid substring because all the 0's (and 1's) are not grouped together. Example 2: Input: "10101" Output: 4 Explanation: There are 4 substrings: "10", "01", "10", "01&
Read more

Count Vowels Permutation: Standard DP

-
Image
Standard DP problem:  https://leetcode.com/problems/count-vowels-permutation/ Given an integer  n , your task is to count how many strings of length  n  can be formed under the following rules: Each character is a lower case vowel ( 'a' ,  'e' ,  'i' ,  'o' ,  'u' ) Each vowel  'a'  may only be followed by an  'e' . Each vowel  'e'  may only be followed by an  'a'  or an  'i' . Each vowel  'i'   may not  be followed by another  'i' . Each vowel  'o'  may only be followed by an  'i'  or a  'u' . Each vowel  'u'  may only be followed by an  'a'. Since the answer may be too large, return it modulo  10^9 + 7. Example 1: Input: n = 1 Output: 5 Explanation: All possible strings are: "a", "e", "i" , "o" and "u". Example 2: Input: n = 2 Output: 10 Explanation: All possible strings are
Read more

Maximum Number of Balloons

-
Image
#431 in my solved list:  https://leetcode.com/problems/maximum-number-of-balloons/ Given a string  text , you want to use the characters of  text  to form as many instances of the word  "balloon"  as possible. You can use each character in  text   at most once . Return the maximum number of instances that can be formed.   Example 1: Input: text = "nlaebolko" Output: 1 Example 2: Input: text = "loonbalxballpoon" Output: 2 Example 3: Input: text = "leetcode" Output: 0 Constraints: 1 <= text.length <= 10^4 text  consists of lower case English letters only. Solution is as follows:  - Count the number of occurrences of the "balloon" letters in the input string  - For "l" and "o", divide the count by 2  - If the balloon string is not fully covered, return 0  - Return the min number across all occurrences Code is below, cheers, ACC. public class Solution {     public int M
Read more