Dot Product of Two Sparse Vectors

Author: anantkaushik

1570-dot-product-of-two-sparse-vectors.py

@@ -0,0 +1,78 @@
+"""
+Problem Link: https://leetcode.com/problems/dot-product-of-two-sparse-vectors/
+
+Given two sparse vectors, compute their dot product.
+Implement class SparseVector:
+SparseVector(nums) Initializes the object with the vector nums
+dotProduct(vec) Compute the dot product between the instance of SparseVector and vec
+A sparse vector is a vector that has mostly zero values, you should store the sparse 
+vector efficiently and compute the dot product between two SparseVector.
+Follow up: What if only one of the vectors is sparse?
+
+Example 1:
+Input: nums1 = [1,0,0,2,3], nums2 = [0,3,0,4,0]
+Output: 8
+Explanation: v1 = SparseVector(nums1) , v2 = SparseVector(nums2)
+v1.dotProduct(v2) = 1*0 + 0*3 + 0*0 + 2*4 + 3*0 = 8
+
+Example 2:
+Input: nums1 = [0,1,0,0,0], nums2 = [0,0,0,0,2]
+Output: 0
+Explanation: v1 = SparseVector(nums1) , v2 = SparseVector(nums2)
+v1.dotProduct(v2) = 0*0 + 1*0 + 0*0 + 0*0 + 0*2 = 0
+
+Example 3:
+Input: nums1 = [0,1,0,0,2,0,0], nums2 = [1,0,0,0,3,0,4]
+Output: 6
+
+Constraints:
+n == nums1.length == nums2.length
+1 <= n <= 10^5
+0 <= nums1[i], nums2[i] <= 100
+"""
+class SparseVector:
+ def __init__(self, nums: List[int]):
+ self.non_zeroes = []
+ for index, num in enumerate(nums):
+ if num != 0:
+ self.non_zeroes.append([index, num])
+
+ # Return the dotProduct of two sparse vectors
+ def dotProduct(self, vec: 'SparseVector') -> int:
+ prod = 0
+ index1 = index2 = 0
+ 
+ while index1 < len(self.non_zeroes) and index2 < len(vec.non_zeroes):
+ if self.non_zeroes[index1][0] == vec.non_zeroes[index2][0]:
+ prod += (self.non_zeroes[index1][1] * vec.non_zeroes[index2][1])
+ index1 += 1
+ index2 += 1
+ elif self.non_zeroes[index1][0] < vec.non_zeroes[index2][0]:
+ index1 += 1
+ else:
+ index2 += 1
+ 
+ return prod
+
+ 
+class SparseVector1:
+ def __init__(self, nums: List[int]):
+ self.non_zeroes = {}
+ for index, num in enumerate(nums):
+ if num != 0:
+ self.non_zeroes[index] = num
+
+ # Return the dotProduct of two sparse vectors
+ def dotProduct(self, vec: 'SparseVector') -> int:
+ prod = 0
+ for index, num in self.non_zeroes.items():
+ if index in vec.non_zeroes:
+ prod += (vec.non_zeroes[index] * num)
+ 
+ return prod
+ 
+
+# Your SparseVector object will be instantiated and called as such:
+# v1 = SparseVector(nums1)
+# v2 = SparseVector(nums2)
+# ans = v1.dotProduct(v2)