on one's own; by oneself; alone
Emphasizes doing something without help or company. Often used with で as an adverbial phrase.
He solved the problem on his own.
I like traveling by myself.
一人で simply means 'alone' or 'by oneself', while 自分一人 emphasizes the self-reliance aspect more strongly.
独力で is more formal and stresses 'with one's own power/effort', often used in written or formal contexts.
Standard kanji spelling.
Mixed kanji-kana spelling, common in everyday writing.
Uses the less common 独り kanji for ひとり; may appear in literary contexts.
Compound of 自分 (self) and 一人 (one person). The phrase is transparent and follows regular Japanese compounding.