Compute the Indices of the Target Element in Array/List using Py
- 时间:2020-09-13 14:33:25
- 分类:网络文摘
- 阅读:121 次
Given an array (or list), and a target element, find all the indices that the element appears in it. For example,
Array: [1, 2, 3, 4, 5, 5, 6, 7, 8], and find the element 5, which appears in index 4 and 5, thus return [4, 5].
This is a trivial question and most programmers know how to do this using a for loop. For example,
In Python:
1 2 3 4 5 6 | def getIndices(data, element): x = [] for i in range(len(data)): if data[i] == element: x.append(i) return x |
def getIndices(data, element): x = [] for i in range(len(data)): if data[i] == element: x.append(i) return x
Or similarly in Javascript:
1 2 3 4 5 6 7 8 9 | function getIndices(data, element) { let x = []; for (let i = 0; i < data.length; i += 1) { if (data[i] === element) { x.push(i); } } return x; } |
function getIndices(data, element) { let x = []; for (let i = 0; i < data.length; i += 1) { if (data[i] === element) { x.push(i); } } return x; }
However, as a spirit of avoiding loops as much as you can, we can simplify the implementation. In Python, we can use the enumerate and the list comprehension which gives us the following short and concise solution to return the list of the indices for a target element in the array.
1 2 | def getIndices(data, element): return [x for x, y in enumerate(data) if y == element] |
def getIndices(data, element): return [x for x, y in enumerate(data) if y == element]
In Javascript, we could similarly implement a enumerate function, alternatively, we can chain map and filter function.
1 2 3 4 5 6 7 8 | function getIndices(data, element) { let i = -1; return data.map(x => { i ++; // incrementing the index // return index for target element return x == element ? i : false; }).filter(x => typeof x !== 'boolean'); } |
function getIndices(data, element) { let i = -1; return data.map(x => { i ++; // incrementing the index // return index for target element return x == element ? i : false; }).filter(x => typeof x !== 'boolean'); }
The map function maps those target elements with their indices, and others similar set to false – which will be filtered out via filter.
–EOF (The Ultimate Computing & Technology Blog) —
推荐阅读:The Common Kodi Errors and Use of Free VPN for Linux Java Pattern: Use Atomic Boolean to Return Single Usage Object Significance of HTML and CSS in Mobile App Development How to Reverse Words in a String using Modern Programming Langua The Python Function to Retrieve the Producer Reward for Witness Function to Compute the Average Salary Excluding the Minimum and Efficient Algorithms to Compute The kth Factor of a Natural Numb Can We Make Arithmetic Progression From Sequence of Numbers? How to SSH to Remote Host using the Priviate/Public Keys Authent How do you Test Getter and Setter Interface in Java using Mockit
- 评论列表
-
- 添加评论