Number of Islands

mediumGraphs+20 XPTime limit 2s

A grid has land (1) and water (0). An island is a group of land cells connected up, down, left or right. Count the islands.

Input:

line 1: r c (rows, columns)
next r lines: a string of c characters, each 0 or 1

Output: the number of islands.

Constraints: 1 ≤ r, c ≤ 500. Large grids can be one big island — an iterative DFS/BFS avoids deep recursion.

Sample input 1

Sample output 1

Sample input 2

Sample output 2

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Read input from standard input and print the answer to standard output. Your code runs in a secure sandbox against the samples (Run) and hidden tests (Submit).

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