Create 311-sparse-matrix-multiplication.js

Author: everthis

311-sparse-matrix-multiplication.js

@@ -0,0 +1,49 @@
+/**
+
+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 = function(A, B) {
+  const aLen = A.length, bLen = B.length
+  if(aLen === 0 || bLen === 0) return []
+  const aCol = A[0].length, bCol = B[0].length
+  const res = Array.from({ length: aLen }, () => new Array(bCol).fill(0))
+  for(let i = 0; i < aLen; i++) {
+    for(let j = 0; j < bCol; j++) {
+      let tmp = 0
+      for(let k = 0; k < bLen; k++) {
+        tmp += A[i][k] * B[k][j]
+      }
+      res[i][j] = tmp
+    }
+  }
+  return res
+};