Here are two parse trees for string if ( true ) if (true) x else x.
---S--- /| | |\ / | | | \ / | | | \ / | | | \ if ( E ) ------S------- | /| | | | | \ true / | | | | | \ / | | | | | \ if ( E ) S else S | | | true x x ------S------- /| | | | | \ / | | | | | \ / | | | | | \ if ( E ) | else S | | | true | x ---S--- /| | |\ / | | | \ / | | | \ / | | | \ if ( E ) S | | true x