Sparse Matrix Multiplication

Author: jeantimex

README.md

@@ -94,6 +94,7 @@ A collection of JavaScript problems and solutions for studying algorithms.
 - [Diagonal Traverse](src/matrix/diagonal-traverse.js)
 - [Number Of Corner Rectangles](src/matrix/number-of-corner-rectangles.js)
 - [Lonely Pixel I](src/matrix/lonely-pixel-i.js)
+- [Sparse Matrix Multiplication](src/matrix/sparse-matrix-multiplication.js)
 
 ### String
 

src/matrix/sparse-matrix-multiplication.js

@@ -0,0 +1,59 @@
+/**
+ * Sparse Matrix Multiplication
+ *
+ * Given two sparse matrices A and B, return the result of AB.
+ *
+ * You may assume that A's column number is equal to B's row number.
+ *
+ * Example:
+ *
+ * Input:
+ *
+ * A = [
+ *   [ 1, 0, 0],
+ *   [-1, 0, 3]
+ * ]
+ *
+ * B = [
+ *   [ 7, 0, 0 ],
+ *   [ 0, 0, 0 ],
+ *   [ 0, 0, 1 ]
+ * ]
+ *
+ * Output:
+ *
+ *      |  1 0 0 |   | 7 0 0 |   |  7 0 0 |
+ * AB = | -1 0 3 | x | 0 0 0 | = | -7 0 3 |
+ *                   | 0 0 1 |
+ */
+
+/**
+ * @param {number[][]} A
+ * @param {number[][]} B
+ * @return {number[][]}
+ */
+const multiply = (A, B) => {
+  const mA = A.length;
+  const nA = A[0].length;
+  const nB = B[0].length;
+
+  const C = Array(mA)
+    .fill()
+    .map(() => Array(nB).fill(0));
+
+  for (let i = 0; i < mA; i++) {
+    for (let k = 0; k < nA; k++) {
+      if (A[i][k] !== 0) {
+        for (let j = 0; j < nB; j++) {
+          if (B[k][j] != 0) {
+            C[i][j] += A[i][k] * B[k][j];
+          }
+        }
+      }
+    }
+  }
+
+  return C;
+};
+
+export { multiply };