Added medium/matrix_spiral

bradhanson · bradhanson · commit 14bff41b587e · 2018-07-24T10:39:49.000-04:00
diff --git a/medium/matrix_spiral.js b/medium/matrix_spiral.js
@@ -0,0 +1,80 @@
+/**
+ * Using the JavaScript language, have the function matrixSpiral(strArr) read
+ * the array of strings stored in strArr which will represent a 2D N matrix, and
+ * your program should return the elements after printing them in a clockwise,
+ * spiral order. You should return the newly formed list of elements as a string
+ * with the numbers separated by commas. For example: if strArr is "[1, 2, 3]",
+ * "[4, 5, 6]", "[7, 8, 9]" then this looks like the following 2D matrix:
+ *
+ * 1 2 3
+ * 4 5 6
+ * 7 8 9
+ *
+ * So your program should return the elements of this matrix in a clockwise,
+ * spiral order which is: 1,2,3,6,9,8,7,4,5
+ *
+ * https://www.coderbyte.com/results/bhanson:Matrix%20Spiral:JavaScript
+ *
+ * @param  {array} strArr
+ * @return {string}
+ */
+function matrixSpiral(strArr) {
+    const matrix = strArr.map(JSON.parse);
+
+    const results = [];
+
+    for (const element of matrixSpiralGenerator(matrix)) {
+        results.push(element);
+    }
+
+    return results.join(',');
+}
+
+function* matrixSpiralGenerator(matrix) {
+    // RIGHT 0 -> DOWN 1 -> LEFT 2 -> UP 3
+    const DIRECTIONS = [
+        [1, 0], // RIGHT
+        [0, 1], // DOWN
+        [-1, 0], // LEFT
+        [0, -1] // UP
+    ];
+
+    const visited = Array(matrix.length)
+        .fill(0)
+        .map(row => Array(matrix[0].length).fill(0));
+
+    const totalElements = matrix.length * matrix[0].length;
+
+    let posX = 0;
+    let posY = 0;
+
+    let vector = 0; // index of DIRECTIONS
+
+    yield matrix[posY][posX];
+    visited[posY][posX] = 1;
+
+    for (let i = 1; i < totalElements; i++) {
+        for (let j = 0; j < DIRECTIONS.length; j++) {
+            let testX = posX + DIRECTIONS[vector][0];
+            let testY = posY + DIRECTIONS[vector][1];
+
+            if (
+                testX < visited[0].length &&
+                testY < visited.length &&
+                visited[testY][testX] === 0
+            ) {
+                // Good!
+                posX = testX;
+                posY = testY;
+                visited[posY][posX] = 1;
+                break;
+            }
+            // Try next direction
+            vector = (vector + 1) % 4;
+        }
+
+        yield matrix[posY][posX];
+    }
+}
+
+module.exports = matrixSpiral;
diff --git a/medium/matrix_spiral.test.js b/medium/matrix_spiral.test.js
@@ -0,0 +1,27 @@
+const matrixSpiral = require('./matrix_spiral');
+
+describe('matrixSpiral()', () => {
+    test('returns correct matrix spiral', () => {
+        expect(matrixSpiral(['[1, 2, 3]', '[4, 5, 6]', '[7, 8, 9]'])).toBe(
+            '1,2,3,6,9,8,7,4,5'
+        );
+
+        expect(matrixSpiral(['[1, 2]', '[10, 14]'])).toBe('1,2,14,10');
+
+        expect(
+            matrixSpiral(['[4, 5, 6, 5]', '[1, 1, 2, 2]', '[5, 4, 2, 9]'])
+        ).toBe('4,5,6,5,2,9,2,4,5,1,1,2');
+    });
+
+    test('passes Coderbyte.com tests', () => {
+        expect(
+            matrixSpiral([
+                '[1, 2, 3, 4, 5]',
+                '[4, 5, 6, 7, 8]',
+                '[7, 8, 9, 10, 11]',
+                '[14, 3, 2, 1, 3]',
+                '[6, 7, 3, 2, 1]'
+            ])
+        ).toBe('1,2,3,4,5,8,11,3,1,2,3,7,6,14,7,4,5,6,7,10,1,2,3,8,9');
+    });
+});
