# 1507. Dot Product of Two Sparse Vectors
###### tags: `Leetcode` `FaceBook` `Medium`
Link: https://leetcode.com/problems/dot-product-of-two-sparse-vectors/
## Code

class SparseVector {
    Map<Integer, Integer> mapping;
    SparseVector(int[] nums) {
        mapping = new HashMap<Integer, Integer>();
        for(int i = 0;i < nums.length;i++){
            if(nums[i]!=0){
                mapping.put(i,nums[i]);
            }
        }
    }
    
	// Return the dotProduct of two sparse vectors
    public int dotProduct(SparseVector vec) {
        int result = 0;
        for(int i:this.mapping.keySet()){
            if(vec.mapping.containsKey(i)){
                result+=mapping.get(i)*vec.mapping.get(i);
            }
        }
        return result;
    }
}