Richest Customer Wealth

Sum each row once\n\nEach row represents one customer, so keep best = 0 (or negative infinity if balances may be negative). For every row, reset wealth = 0, add each account balance in that row, then set best = max(best, wealth). The invariant is that after processing a row, best equals the largest complete customer total seen so far. There is no reason to sort totals, allocate another array, or compare account values individually because the objective is the row sum. If the contract permits an empty matrix, clarify whether the answer should be zero or absent; common versions have at least one customer and account. For an m x n matrix, the algorithm is O(mn) time and O(1) extra space. Test one customer, one account per customer, equal totals, zero balances, and values large enough that the running sum needs a wider integer type.