1331. Array sequence number conversion: simple simulation question

Title Description

This is a LeetCode Upper 1331. Array number conversion , The difficulty is Simple .

Tag : 「 simulation 」、「 Hashtable 」、「 Sort 」

Give you an array of integers  arr, Please replace each element in the array with their ordinal number after sorting .

The serial number represents how big an element is . The rules for serial numbers are as follows ：

• The serial number from Numbered starting .
• The bigger an element is , So the bigger the serial number . If two elements are equal , So they have the same serial number .
• The serial number of each number should be as small as possible .

Example 1：

 Input ：arr = [40,10,20,30]

 Output ：[4,1,2,3]

 explain ：40  It's the biggest element . 10  It's the smallest element . 20  It's the second smallest number . 30  It's the third smallest number .

Example 2：

 Input ：arr = [100,100,100]

 Output ：[1,1,1]

 explain ： All elements have the same sequence number .

Example 3：

 Input ：arr = [37,12,28,9,100,56,80,5,12]

 Output ：[5,3,4,2,8,6,7,1,3]

Tips ：

simulation

Simulate according to the meaning of the question .

Yes arr Copy to get a new array clone, Yes clone Array to sort , Then use the hash table to record the mapping relationship between elements and sequence numbers , Finally, the answer is constructed according to the mapping relationship .

Java Code ：

class Solution {
    
    public int[] arrayRankTransform(int[] arr) {
    
        int[] clone = arr.clone();
        Arrays.sort(clone);
        Map<Integer, Integer> map = new HashMap<>();
        int n = arr.length, idx = 0;
        for (int i : clone) {
    
            if (!map.containsKey(i)) map.put(i, ++idx);
        }
        int[] ans = new int[n];
        for (int i = 0; i < n; i++) ans[i] = map.get(arr[i]);
        return ans;
    }
}

TypeScript Code ：

function arrayRankTransform(arr: number[]): number[] {
    
    let clone = new Array<number>()
    for (const i of arr) clone.push(i)
    clone.sort((a,b)=>a-b)
    let n = arr.length, idx = 0
    let map = new Map<number, number>()
    for (const i of clone) {
    
        if (!map.has(i)) map.set(i, ++idx)
    }
    let ans = new Array<number>()
    for (let i = 0; i < n; i++) ans.push(map.get(arr[i]))
    return ans
};

• Time complexity ：
• Spatial complexity ：

Last

This is us. 「 Brush through LeetCode」 The first of the series No.1331 piece , The series begins with 2021/01/01, As of the start date LeetCode I have in common 1916 questions , Part of it is a locked question , We will finish all the questions without lock first .

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