number_of_islands

// edge cases: no islands, all zeros
// constraints: none


// start with first row
  // walk through each index in the row 
    // if it sees a 1
        // check each potential island in array
            // check each coordinate 
               // determine if the stored coordinate is adjacent to the current coordinate
                  // if so add that coordinate to that array
                     // check if there are any matches in the matching array
                       // if there are, join the arrays
                         // create a new array with all coordinates from both arrays
                         // slice out the other matching array
                         // add new array index to matches
                       // otherwise add index to array of matches for this coordinate
                  // otherwise add it to a new potential island array

  // continue until all rows are checked

// return the size of the final array

/*
Input: grid = [
  ["1","1","0","0","0"],
  ["1","1","0","0","0"],
  ["0","0","1","0","0"],
  ["0","0","0","1","1"]
]
Output: 3
*/