Sparse Vector Addition

Large vectors are often stored as linked lists of (index, value) pairs to save space, keeping only non-zero entries. Given two such linked lists (sorted by index), add them together. If an index exists in both, sum their values. If the sum is zero, remove the node. The result must be sorted by index. Input: 1. A line of 'index:value' pairs for Vector A. 2. A line of 'index:value' pairs for Vector B. Output: Space-separated 'index:value' pairs of the resulting vector. Example: Input: 0:5 3:10 5:2 2:4 3:-10 5:8 Output: 0:5 2:4 5:10