View Compilation Error

0_0_5410550_9156.cpp: In function `int main()':
0_0_5410550_9156.cpp:41: error: `island' undeclared (first use this function)
0_0_5410550_9156.cpp:41: error: (Each undeclared identifier is reported only once for each function it appears in.)
0_0_5410550_9156.cpp:46: error: `visited' undeclared (first use this function)
0_0_5410550_9156.cpp:48: error: `S_set' undeclared (first use this function)