diff --git a/chapter12.tex b/chapter12.tex
index fe77bac..5cf87bc 100644
--- a/chapter12.tex
+++ b/chapter12.tex
@@ -331,7 +331,7 @@ and the array \texttt{e} will contain the
 distances to all nodes in the graph.
 The search can be implemented as follows:
 \begin{lstlisting}
-z[s] = 1; e[x] = 0;
+z[x] = 1; e[x] = 0;
 q.push(x);
 while (!q.empty()) {
     int s = q.front(); q.pop();
@@ -546,4 +546,4 @@ it is difficult to find out if the nodes
 in a graph can be colored using $k$ colors
 so that no adjacent nodes have the same color.
 Even when $k=3$, no efficient algorithm is known
-but the problem is NP-hard.
\ No newline at end of file
+but the problem is NP-hard.