1331. Rank Transform of an Array

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

这题我直接偷懒了，使用set的特性去重，然后进行索引的分配，当然时间和空间复杂度没法看。

class RankTransformOfAnArray : public Solution {
public:
    void Exec() {
        auto res = arrayRankTransform(vector<int>{40,10,20,30});
    }
    vector<int> arrayRankTransform(const vector<int>& arr) {
        unordered_map<int, int> ranks;
        set<int> rankset;
        for (auto v : arr) {
            rankset.insert(v);
        }
        int index = 1;
        for (auto v : rankset) {
            ranks[v] = index++;
        }
        vector<int> res;
        for (auto &v : arr) {
            res.push_back(ranks[v]);
        }
        return res;
    }
};