Given an array of integers arr, replace each element with its rank.
The rank represents how large the element is. The rank has the following rules:
Rank is an integer starting from 1.
The larger the element, the larger the rank. If two elements are equal, their rank must be the same.
Rank should be as small as possible.
Example 1:
Input: arr = [40,10,20,30]
Output: [4,1,2,3]
Explanation: 40 is the largest element. 10 is the smallest. 20 is the second smallest. 30 is the third smallest.
Example 2:
Input: arr = [100,100,100]
Output: [1,1,1]
Explanation: Same elements share the same rank.
Example 3:
Input: arr = [37,12,28,9,100,56,80,5,12]
Output: [5,3,4,2,8,6,7,1,3]
Constraints:
0 <= arr.length <= 105
-109 <= arr[i] <= 109
Solution:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
namespace LeetCode.AskGif.Easy.Array
{
public class ArrayRankTransformSoln
{
public int[] ArrayRankTransform(int[] arr)
{
var map = new Dictionary<int, int>();
var mapRank = new Dictionary<int, int>();
for (int i = 0; i < arr.Length; i++)
{
if (map.ContainsKey(arr[i]))
{
map[arr[i]]++;
}
else
{
map.Add(arr[i], 1);
}
}
var sorted = map.OrderBy(x => x.Key);
var rank = 1;
foreach (var item in sorted)
{
mapRank.Add(item.Key, rank);
rank++;
}
var res = new int[arr.Length];
for (int i = 0; i < arr.Length; i++)
{
res[i] = mapRank[arr[i]];
}
return res;
}
}
}
Time Complexity: O(n)
Space Complexity: O(n)
Unit Tests:
using LeetCode.AskGif.Easy.Array;
using Microsoft.VisualStudio.TestTools.UnitTesting;
using System;
using System.Collections.Generic;
using System.Text;
namespace CodingUnitTest.Easy.Array
{
[TestClass]
public class ArrayRankTransformSolnTests
{
[TestMethod]
public void ArrayRankTransformSoln_First()
{
var arr = new int[] { 40, 10, 20, 30 };
var output = new int[]{ 4, 1, 2, 3 };
var res = new ArrayRankTransformSoln().ArrayRankTransform(arr);
AreEqual(res, output);
}
[TestMethod]
public void ArrayRankTransformSoln_Second()
{
var arr = new int[] { 100, 100, 100 };
var output = new int[] { 1, 1, 1 };
var res = new ArrayRankTransformSoln().ArrayRankTransform(arr);
AreEqual(res, output);
}
[TestMethod]
public void ArrayRankTransformSoln_Third()
{
var arr = new int[] { 37, 12, 28, 9, 100, 56, 80, 5, 12 };
var output = new int[] { 5, 3, 4, 2, 8, 6, 7, 1, 3 };
var res = new ArrayRankTransformSoln().ArrayRankTransform(arr);
AreEqual(res, output);
}
private void AreEqual(int[] res, int[] output)
{
Assert.AreEqual(res.Length, output.Length);
for (int i = 0; i < res.Length; i++)
{
Assert.AreEqual(res[i], output[i]);
}
}
}
}
