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Formatted question description: https://leetcode.ca/all/1331.html

1331. Rank Transform of an Array (Easy)

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

Related Topics:
Array

Solution 1.

  • class Solution {
    public int[] arrayRankTransform(int[] arr) {
        Set<Integer> set = new HashSet<Integer>();
        for (int num : arr)
            set.add(num);
        List<Integer> list = new ArrayList<Integer>();
        for (int num : set)
            list.add(num);
        Collections.sort(list);
        Map<Integer, Integer> numRankMap = new HashMap<Integer, Integer>();
        int size = list.size();
        for (int i = 0; i < size; i++) {
            int num = list.get(i);
            numRankMap.put(num, i + 1);
        }
        int length = arr.length;
        int[] ranks = new int[length];
        for (int i = 0; i < length; i++) {
            int num = arr[i];
            int rank = numRankMap.get(num);
            ranks[i] = rank;
        }
        return ranks;
    }
}

############

class Solution {
    public int[] arrayRankTransform(int[] arr) {
        Set<Integer> s = new HashSet<>();
        for (int v : arr) {
            s.add(v);
        }
        List<Integer> alls = new ArrayList<>(s);
        alls.sort((a, b) -> a - b);
        Map<Integer, Integer> m = new HashMap<>();
        for (int i = 0; i < alls.size(); ++i) {
            m.put(alls.get(i), i + 1);
        }
        int[] ans = new int[arr.length];
        for (int i = 0; i < arr.length; ++i) {
            ans[i] = m.get(arr[i]);
        }
        return ans;
    }
}

  • // OJ: https://leetcode.com/problems/rank-transform-of-an-array/
// Time: O(NlogN)
// Space: O(N)
class Solution {
public:
    vector<int> arrayRankTransform(vector<int>& arr) {
        set<int> s(arr.begin(), arr.end());
        unordered_map<int, int> m;
        vector<int> ans(arr.size(), 0);
        int i = 0;
        for (auto it = s.begin(); it != s.end(); ++it) m[*it] = ++i;
        for (int j = 0; j < arr.size(); ++j) ans[j] = m[arr[j]];
        return ans;
    }
};

  • class Solution:
    def arrayRankTransform(self, arr: List[int]) -> List[int]:
        m = {v: i for i, v in enumerate(sorted(set(arr)), 1)}
        return [m[v] for v in arr]



  • func arrayRankTransform(arr []int) []int {
	s := make(map[int]bool)
	for _, v := range arr {
		s[v] = true
	}
	var alls []int
	for v := range s {
		alls = append(alls, v)
	}
	sort.Ints(alls)
	m := make(map[int]int)
	for i, v := range alls {
		m[v] = i + 1
	}
	var ans []int
	for _, v := range arr {
		ans = append(ans, m[v])
	}
	return ans
}

  • function arrayRankTransform(arr: number[]): number[] {
    const t = [...arr].sort((a, b) => a - b);
    let m = 0;
    for (let i = 0; i < t.length; ++i) {
        if (i === 0 || t[i] !== t[i - 1]) {
            t[m++] = t[i];
        }
    }
    const search = (t: number[], right: number, x: number) => {
        let left = 0;
        while (left < right) {
            const mid = (left + right) >> 1;
            if (t[mid] > x) {
                right = mid;
            } else {
                left = mid + 1;
            }
        }
        return left;
    };
    const ans: number[] = [];
    for (const x of arr) {
        ans.push(search(t, m, x));
    }
    return ans;
}

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