CF1829E.The Lakes

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 $a_{i,j} \gt 0$, 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.

给你一个 $n \times m$ 的非负整数网格 $a$。其中 $a_{i,j}$ 表示第 $i$ 行、第 $j$ 列处的水深。

一个“湖泊”是指满足以下条件的一组格子：

• 该集合中的每个格子均满足 $a_{i,j} > 0$；
• 集合中任意两个格子之间均存在一条路径（仅允许向上、向下、向左或向右移动若干次），且路径上所有经过的格子均满足 $a_{i,j} > 0$。

一个湖泊的体积定义为该湖泊中所有格子水深之和。

请找出网格中体积最大的湖泊的体积。

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 $10^6$.

第一行包含一个整数 $t$（$1 \leq t \leq 10^4$）—— 测试用例的数量。

每个测试用例的第一行包含两个整数 $n, m$（$1 \leq n, m \leq 1000$）—— 网格的行数和列数。

接下来是 $n$ 行，每行包含 $m$ 个整数 $a_{i,j}$（$0 \leq a_{i,j} \leq 1000$）—— 每个单元格中水的深度。

保证所有测试用例中 $n \cdot m$ 的总和不超过 $10^6$。

For each test case, output a single integer — the largest volume of a lake in the grid.

对于每个测试用例，输出一个整数——网格中湖泊的最大体积。