Binary trees can also be stored in breadth-first order as an implicit data structure in arrays, and if the tree is a complete binary tree, this method wastes no space. In this compact arrangement, if a node has an index i, its children are found at indices (for the left child) and (for the right), while its parent (if any) is found at index (assuming the root has index zero). Alternatively, with a 1-indexed array, the implementation is simplified with children found at and , and parent found at .
Binary trees can also be stored in breadth-first order as an implicit data structure in arrays, and if the tree is a complete binary tree, this method wastes no space. In this compact arrangement, if a node has an index i its children are found at indices (for the left child) and (for the right), while its parent (if any) is found at index (assuming the root has index zero). Alternatively, with a 1-indexed, array, the implementation is simplified with children found at and , and parent found at .