E. The Lakes
dfs and similar; dsu; graphs; implementation
You are given an \(n \times m\) grid \(a\) of non-negative integers. The value \(a_{i,j}\) represents the depth of water at the \(i\)-th row and \(j\)-th column. A lake is a set of cells such that: each cell in the set has \(a_{i,j} > 0\), and there exists a path between any pair of cells in the lake by going up, down, left, or right a number of times and without stepping on a cell with \(a_{i,j} = 0\). The volume of a lake is the sum of depths of all the cells in the lake.Find the largest volume of a lake in the grid.
The first line contains a single integer \(t\) (\(1 \leq t \leq 10^4\)) — the number of test cases.The first line of each test case contains two integers \(n, m\) (\(1 \leq n, m \leq 1000\)) — the number of rows and columns of the grid, respectively.Then \(n\) lines follow each with \(m\) integers \(a_{i,j}\) (\(0 \leq a_{i,j} \leq 1000\)) — the depth of the water at each cell.It is guaranteed that the sum of \(n \cdot m\) over all test cases does not exceed \(10^6\).
For each test case, output a single integer — the largest volume of a lake in the grid.