add day 27

Author: MadhavBahl

README.md

@@ -50,6 +50,7 @@ Read [CONTRIBUTING.md](./CONTRIBUTING.md) for contribution guidelines.
 24. [Day 24 -- Array Circular Rotation](./day24) -- [http://codetoexpress.tech/dc/day24/](http://codetoexpress.tech/dc/day24/)
 25. [Day 25 -- Rotate Square Tile](./day25) -- [http://codetoexpress.tech/dc/day25/](http://codetoexpress.tech/dc/day25/)
 26. [Day 26 -- Spiral Generation and Copy](./day26) -- [http://codetoexpress.tech/dc/day26/](http://codetoexpress.tech/dc/day26/)
+27. [Day 27 -- The Minesweeper Problem](./day27) -- [http://codetoexpress.tech/dc/day27/](http://codetoexpress.tech/dc/day27/)
 
 ## [More Problems](./BONUS/README.md)
 

day27/README.md

@@ -0,0 +1,124 @@
+![cover](./cover.png)
+
+# Day 27 - Array Series Part 10: The Minesweeper Problem
+
+**Question** -- Given the position of bombs, number of rows and number of columns, prepare the mine field for the minesweeper game.
+
+**Example**
+
+```
+input:
+    position of bombs - [[0, 0], [0, 1]]
+    number of columns in mine field = 4
+    number of rows in mine field = 4
+output:
+[
+    [-1, -1, 1, 0],
+    [ 2,  2, 1, 0],
+    [ 0,  0, 0, 0],
+    [ 0,  0, 0, 0]
+]
+```
+
+**Please Note that** 
+
+- Positions having -1 represents a bomb
+- 0 indicates **no bomb in vicinity**
+- any other positive number n represents **n bombs in the vicinity**
+
+Vicinity includes direct horizontal/vertical/diagonal neighboring position
+
+![ques](./ques.png)
+
+# Solution
+
+## JavaScript Implementation
+
+### [Solution 1 (First Assign then place values)](./JavaScript/minesweeper.js)
+
+```js
+/**
+ * @author MadhavBahlMD
+ * @date 25/01/2019
+ * Method - First Assign then place values
+ * Complexity - O(row*col)   // row and col are the number of rows and number of columns
+ */
+
+function makeMineField (posArr, row, col) {
+    let mineField = [];
+
+    // initialize the mineField with zeros
+    for (let i=0; i<row; i++) {
+        let thisRow = [];
+        for (let j=0; j<col; j++) 
+            thisRow.push (0);
+        mineField.push (thisRow);
+    }
+
+    // Iterate over position array and put -1 at those positions in the minefield
+    for (let pos of posArr) {
+        mineField [pos[0]][pos[1]] = -1;
+    }
+
+    // Iterate over each element and complete the mine field
+    for (let i=0; i<row; i++) {
+        for (let j=0; j<col; j++) {
+            if (mineField [i][j] !== -1)
+                mineField[i][j] = assignValue (mineField, i, j, row, col);
+        }
+    }
+
+    console.log (mineField);
+}
+
+function assignValue (mineField, thisRow, thisCol, row, col) {
+    let count = 0;
+
+    // Check for bombs in all 3 rows 
+    for (let i=-1; i<=1; i++) 
+        for (let j=-1; j<=1; j++) 
+            if ((thisRow+i >= 0 && thisRow+i < row) && (thisCol+j >= 0 && thisCol+j < col))
+                if (mineField [thisRow+i][thisCol+j] === -1)  count++;
+    
+    return count;
+}
+
+makeMineField ([[0, 0], [0, 1]], 4, 4);
+```
+
+### [Solution 2 (Assign and place values simultaneously)](./JavaScript/minesweeper2.js)
+
+```js
+/**
+ * @author MadhavBahlMD
+ * @date 25/01/2019
+ * Method - First Assign then place values
+ * Complexity - O(num_bombs)   // num_bombs = number of bombs
+ */
+
+function makeMineField (posArr, row, col) {
+    let mineField = [];
+
+    // initialize the mineField with zeros
+    for (let i=0; i<row; i++) {
+        let thisRow = [];
+        for (let j=0; j<col; j++) 
+            thisRow.push (0);
+        mineField.push (thisRow);
+    }
+
+    // Iterate over position array and assign values
+    for (let pos of posArr) {
+        mineField [pos[0]][pos[1]] = -1;
+
+        for (let i=-1; i<=1; i++) 
+            for (let j=-1; j<=1; j++) 
+                if ((pos[0]+i >= 0 && pos[0]+i < row) && (pos[1]+j >= 0 && pos[1]+j < col))
+                    if (mineField [pos[0]+i][pos[1]+j] !== -1)  mineField [pos[0]+i][pos[1]+j]++;
+    }
+
+    console.log (mineField);
+}
+
+makeMineField ([[0, 0], [0, 1]], 4, 4);
+```