public static boolean hasStateAssociatedWithOneAlt(ATNConfigSet configs) {
		Map<ATNState, BitSet> x = getStateToAltMap(configs);
		for (BitSet alts : x.values()) {
			if ( alts.cardinality()==1 ) return true;
		}
		return false;
	}
Get a map from state to alt subset from a configuration set. For each
configuration {@code c} in {@code configs}:

<pre>
map[c.{@link ATNConfig#state state}] U= c.{@link ATNConfig#alt alt}
</pre>
runtime/Java/src/org/antlr/v4/runtime/atn/PredictionMode.java