Solution.ts

function jsonToMatrix(arr: any[]): (string | number | boolean | null)[] {
    const dfs = (key: string, obj: any) => {
        if (
            typeof obj === 'number' ||
            typeof obj === 'string' ||
            typeof obj === 'boolean' ||
            obj === null
        ) {
            return { [key]: obj };
        }
        const res: any[] = [];
        for (const [k, v] of Object.entries(obj)) {
            const newKey = key ? `${key}.${k}` : `${k}`;
            res.push(dfs(newKey, v));
        }
        return res.flat();
    };

    const kv = arr.map(obj => dfs('', obj));
    const keys = [
        ...new Set(
            kv
                .flat()
                .map(obj => Object.keys(obj))
                .flat(),
        ),
    ].sort();
    const ans: any[] = [keys];
    for (const row of kv) {
        const newRow: any[] = [];
        for (const key of keys) {
            const v = row.find(r => r.hasOwnProperty(key))?.[key];
            newRow.push(v === undefined ? '' : v);
        }
        ans.push(newRow);
    }
    return ans;
}