LeetCode[200] 岛屿数量

Related Topics:
“深度优先搜索”: https://leetcode.com/tag/depth-first-search/
“广度优先搜索”: https://leetcode.com/tag/breadth-first-search/
“并查集”: https://leetcode.com/tag/union-find/
“数组”: https://leetcode.com/tag/array/
“矩阵”: https://leetcode.com/tag/matrix/
Similar Questions:
“被围绕的区域”: https://leetcode.com/problems/surrounded-regions/
“墙与门”: https://leetcode.com/problems/walls-and-gates/
“岛屿数量 II”: https://leetcode.com/problems/number-of-islands-ii/
“无向图中连通分量的数目”: https://leetcode.com/problems/number-of-connected-components-in-an-undirected-graph/
“不同岛屿的数量”: https://leetcode.com/problems/number-of-distinct-islands/
“岛屿的最大面积”: https://leetcode.com/problems/max-area-of-island/

Problem:

给你一个由 '1'（陆地）和 '0'（水）组成的的二维网格，请你计算网格中岛屿的数量。

岛屿总是被水包围，并且每座岛屿只能由水平方向和/或竖直方向上相邻的陆地连接形成。

此外，你可以假设该网格的四条边均被水包围。

示例 1：

输入：grid = [
  ["1","1","1","1","0"],
  ["1","1","0","1","0"],
  ["1","1","0","0","0"],
  ["0","0","0","0","0"]
]
输出：1

示例 2：

输入：grid = [
  ["1","1","0","0","0"],
  ["1","1","0","0","0"],
  ["0","0","1","0","0"],
  ["0","0","0","1","1"]
]
输出：3

提示：

• m == grid.length
• n == grid[i].length
• 1 <= m, n <= 300
• grid[i][j] 的值为 '0' 或 `’1’