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Constructing a string based on character matrix and number array in JavaScript
Problem
We are required to write a JavaScript function that takes in an n * n matrix of string characters and an array of integers (positive and unique).
Our function should construct a string of those characters whose 1-based index is present in the array of numbers.
Character Matrix −
[ [‘a’, ‘b’, ‘c’, d’], [‘o’, ‘f’, ‘r’, ‘g’], [‘h’, ‘i’, ‘e’, ‘j’], [‘k’, ‘l’, ‘m’, n’] ];
Number Array −
[1, 4, 5, 7, 11]
Should return ‘adore’ because these are the characters present at the 1-based indices specified by number array in the matrix.
Example
Following is the code −
const arr = [ ['a', 'b', 'c', 'd'], ['o', 'f', 'r', 'g'], ['h', 'i', 'e', 'j'], ['k', 'l', 'm', 'n'] ]; const pos = [1, 4, 5, 7, 11]; const buildString = (arr = [], pos = []) => { const flat = []; arr.forEach(sub => { flat.push(...sub); }); let res = ''; pos.forEach(num => { res += (flat[num - 1] || ''); }); return res; }; console.log(buildString(arr, pos));
Output
Following is the console output −
adore
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