# FAI cheet sheet
Increasing degrees of consistency
* 1-Consistency (Node Consistency): Each single node’s domain has a value which meets that node’s unary constraints
* 2-Consistency (Arc Consistency): For each pair of nodes, any consistent assignment to one can be extended to the other
* K-Consistency: For each k nodes, any consistent assignment to k-1 can be extended to the kth node
* Strong k-consistency: also k-1, k-2, … 1 consistent
* Theorem: if the constraint graph has no loops, the CSP can be solved in $O(nd^2)$

* Should we stop when we enqueue a goal? No: only stop when we dequeue a goal
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