Compute Every Binary Cell Distance to a Zero

### Problem Return a matrix whose entry at each cell is its shortest distance to any zero in mat. Moving to a cell sharing an edge costs one; diagonal moves are not allowed. At least one zero exists. ```cpp class Solution { public: vector<vector<int>> updateMatrix(vector<vector<int>>& mat); }; ``` ### Examples **Example 1:** ```text mat = [[1,1,0]] Output: [[2,1,0]] Explanation: Distances increase along the row away from the zero. ``` **Example 2:** ```text mat = [[0,1],[1,1]] Output: [[0,1],[1,2]] Explanation: The lower-right cell needs two edge moves. ``` ### Constraints - Rectangular m-by-n input: m and n are each in 1..10000, and total cells m*n is in 1..10000. Entries are binary, with at least one zero. ### Clarifying Questions Start from all zeros and count only edge-adjacent moves. ```hint Read the boundary condition Can all zeros act as simultaneous search sources? ``` ### Contract considerations Start from all zeros and count only edge-adjacent moves.