Wrote function to find the 'n'th match of a regex

matching.go

@@ -138,6 +138,27 @@ func pruneIndices(indices []Match) []Match {
 	return toRet
 }
 
+// findNthMatch finds the 'n'th match of the regex represented by the given start-state, with
+// the given string.
+// It returns an error (!= nil) if there are fewer than 'n' matches in the string.
+func findNthMatch(start *State, str []rune, numGroups int, n int) (Match, error) {
+	idx := 0
+	matchNum := 0
+	var matchFound bool
+	var matchIdx Match
+	for idx <= len(str) {
+		matchFound, matchIdx, idx = findAllMatchesHelper(start, str, idx, numGroups)
+		if matchFound {
+			matchNum++
+		}
+		if matchNum == n {
+			return matchIdx, nil
+		}
+	}
+	// We haven't found the nth match after scanning the string - Return an error
+	return nil, fmt.Errorf("Invalid match index. Too few matches found.")
+}
+
 // findAllMatches tries to find all matches of the regex represented by given start-state, with
 // the given string
 func findAllMatches(start *State, str []rune, numGroups int) []Match {