Is live stream me maine Codeforces Round 731 (Div 3) ke A se leke F tak problems ko contest-style flow me discuss kiya—jo solve hua, jis point pe atka, aur jo approach actual me kaam karti hai. Start me setup/intro ke baad maine D se pick kiya ("Growing Sequence" type bitmask/sets wali condition), jahan core idea ye tha: previous element me jo bits set hain, next me bhi set honi chahiye—so main har step pe previous ko carry forward karta hoon, aur current me missing bits ko add kar deta hoon to lexicographically smallest sequence ban jaati hai. Uske baad E (Air Conditioner) me maine typical brute force ko avoid karke left-to-right / right-to-left passes ka logic use kiya. Idea simple hai: har cell ka answer ya to usi cell me AC ka temp hoga, warna nearest AC se distance add karke minimum—so do passes se min nikal jaata hai. F me maine thoda heavy approach bataya: range GCD + binary search + segment tree. Main yahi bolta hoon—standard cheez ko baar-baar reinvent mat karo; segment tree ka basic implementation aata ho to range gcd queries easy ho jaati hain, aur binary search se minimum length/steps find kar lete ho. End me thoda chat + strategy talk bhi hai—practice karo, contest khatam nahi hua, next round me aur clean ho jaayega.