{"blocks": [{"key": "19465386", "text": "Question", "type": "header-two", "depth": 0, "inlineStyleRanges": [], "entityRanges": [], "data": {}}, {"key": "2cd1869f", "text": "Given an expression of lowercase letters, '+', '', and parentheses with no '+' outside any parentheses, return an equivalent expression containing only '+' by fully expanding all products (e.g., (a+b)(c+d) → ac+ad+bc+bd). Achieve O(1) extra-space complexity. Follow-up: If '+' may appear outside parentheses (e.g., a+bc(d+e+f)+k+m*(g+h)+i), output the fully expanded '+'-only form (a+bcd+bce+bcf+k+mg+mh+i). Provide working code that may use O(n) extra space (e.g., a stack).", "type": "unstyled", "depth": 0, "inlineStyleRanges": [], "entityRanges": [], "data": {}}], "entityMap": {}}