639. Richest Customer Wealth
A bank tracks its customers in an m × n grid accounts, where accounts[i][j] is the amount of money customer i keeps in bank j. A customer's wealth is the total across all of their accounts — the sum of row i.
Return the wealth of the richest customer, i.e. the largest row sum in the grid.
Example 1:
Input: accounts = [[2, 8, 7], [7, 1, 3], [1, 9, 5]]
Output: 17
Explanation: Row sums are 2+8+7 = 17, 7+1+3 = 11, and 1+9+5 = 15. Customer 0 is the richest with 17.
Example 2:
Input: accounts = [[1, 5], [7, 3], [3, 5]]
Output: 10
Explanation: The three customers hold 6, 10, and 8 in total; the largest is 10.
Example 3:
Input: accounts = [[1, 2, 3], [3, 2, 1]]
Output: 6
Explanation: Both customers total 6 — ties are fine because only the amount is asked for, not who holds it.
Constraints:
- 1 ≤ m, n ≤ 50
- 1 ≤ accounts[i][j] ≤ 100
Hints:
One customer = one row. The wealth of customer i is simply the sum of row i.
You never need to store all the sums — keep a single running maximum and update it as you finish each row.
▶ Run checks these sample cases. Submit also runs hidden edge cases.
Input: accounts = [[2, 8, 7], [7, 1, 3], [1, 9, 5]]
Expected output: 17