2625. Flatten Deeply Nested Array

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JavaScript

Intuition

Flatten nested array recursively. Each element is either integer or array. Recursive or iterative flattening.

Algorithm

1Recursive: for each item, if array recurse, else add to result.

Common Pitfalls

•Straightforward recursion. Handle arbitrary nesting depth.

2625.ts

TypeScript

type MultiDimensionalArray = (number | MultiDimensionalArray)[];

var flat = function (arr: MultiDimensionalArray, n: number): MultiDimensionalArray {
    function dfs(arr: number | MultiDimensionalArray, n: number) {
        if (typeof arr === 'number') {
            ans.push(arr);
        } else if (n === 0) {
            for (const element of arr) {
                ans.push(element);
            }
        } else {
            for (const element of arr) {
                dfs(element, n - 1);
            }
        }
    }
    const ans: MultiDimensionalArray = [];
    dfs(arr, n);
    return ans;
};

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