我正在开发一个项目,要求我在Java中找到给定图形的最小生成树。我非常喜欢Java noob,因为我主要使用C ++。
我编写了算法,但是有一种独特的输入格式,有点像这样:
0 1:33 2:0 3:12 4:29 5:32 6:22 7:13 8:45 9:21
1 0:6 2:18 3:2 4:26 5:41 6:8 7:47 8:13 9:19
2 0:22 1:28 3:49 4:47 5:5 6:16 7:32 8:5 9:34
3 0:21 1:24 2:2 4:29 5:20 6:39 7:17 8:21 9:3
4 0:27 1:20 2:38 3:4 5:14 6:25 7:0 8:24 9:11
5 0:20 1:7 2:29 3:15 4:3 6:19 7:11 8:19 9:41
6 0:14 1:36 2:6 3:45 4:18 5:33 7:43 8:22 9:36
7 0:25 1:12 2:15 3:45 4:18 5:43 6:41 8:37 9:26
8 0:29 1:44 2:23 3:15 4:34 5:45 6:27 7:29 9:4
9 0:18 1:41 2:20 3:25 4:18 5:10 6:10 7:49 8:42
或者,更清楚地说:
[source-vertex] [destination-vertex]:[weight] [destination-vertex]:[weight] ...
我想知道的是如何阅读这种输入格式?
我想读取每一行,直到文件结束,然后解析每行的数字。
所以你基本上有两个问题:
Reader
并使用属性文本编码从InputStream
读取。根据您的格式读取数据的代码:
File f = ... // file to read
try (BufferedReader reader = new BufferedReader(new InputStreamReader(new FileInputStream(f), StandardCharsets.UTF_8))) {
// regular expression checking the format of each line
Pattern linePattern = Pattern.compile("(\\d+)(?:\\s+(\\d+):(\\d+))*");
// regular expression to find the index (first number) in a line
Pattern indexPattern = Pattern.compile("(\\d+)");
// regular expression to find the vertices (a:b) in a line
Pattern relationPattern = Pattern.compile("(\\d+):(\\d+)");
String line;
while ((line = reader.readLine()) != null) {
if (linePattern.matcher(line).matches()) {
Matcher indexMatcher = indexPattern.matcher(line);
if (indexMatcher.find()) {
int sourceVertex = Integer.parseInt(indexMatcher.group(1));
// do something with the sourceVertex
Matcher relationMatcher = relationPattern.matcher(line);
while (relationMatcher.find()) {
int destinationVertex = Integer.parseInt(relationMatcher.group(1));
int weight = Integer.parseInt(relationMatcher.group(2));
// do something with destinationVertex and weight
}
}
}
}
}
我建议使用Steam API并使用BuferedReader加载文件并唱出lines()方法。这会生成一个Stream,然后您可以根据需要进行操作。