Week 04 mini-challenge algorithm PR

src/count-islands/index.js

@@ -1,3 +1,32 @@
-function countIslands(grid) {}
+const countIslands = grid => {
+
+  // Destroy the islands
+  const purgeIslandsFound = (row, col) => {
+    // Base case
+    if (row < 0 || col < 0 || row >= grid.length || col >= grid[row].length || grid[row][col] == 0) {
+      return;
+    }
+    // mark as visited
+    grid[row][col] = 0;
+
+    // Recursive case for neighbours
+    purgeIslandsFound(row - 1, col); //up
+    purgeIslandsFound(row + 1, col); //down
+    purgeIslandsFound(row, col - 1); //left
+    purgeIslandsFound(row, col + 1); //down
+  }
+
+  // Check for islands in each grids
+  let islands = 0
+  for (let i = 0; i < grid.length; i++) {
+    for (let j = 0; j < grid[i].length; j++) {
+      if (grid[i][j] === 1) {
+        islands++
+        purgeIslandsFound(i, j)
+      }
+    }
+  }
+  return islands
+}
 
 module.exports = countIslands;

src/word-search/index.js

@@ -1,3 +1,36 @@
-function wordSearch(words, word) {}
+const wordSearch = (board, word) => {
+
+  let result = false;
+  const transvereGrid = (row, col, i) => {
+    if (!result) {
+      //base case
+      if (row < 0 || col < 0 || row >= board.length || col >= board[0].length) return;
+      if (board[row][col] != word[i]) return; // wrong character, over
+      if (i == word.length - 1) { // found a correct path
+        result = true;
+        return;
+      }
+      board[row][col] = null; // mark as visited
+
+      //recursive case
+      transvereGrid(row + 1, col, i + 1)
+      transvereGrid(row - 1, col, i + 1)
+      transvereGrid(row, col + 1, i + 1)
+      transvereGrid(row, col - 1, i + 1)
+      board[row][col] = word[i] // reset board
+    }
+  }
+
+  for (let i = 0; i < board.length; i++) {
+    for (let j = 0; j < board[0].length; j++) {
+      if (board[i][j] == word[0]) {
+        transvereGrid(i, j, 0)
+        if (result) return result;
+      }
+    }
+  }
+
+  return result;
+};
 
 module.exports = wordSearch;