如何解析指数的多项式

Question

If given a String such as "(-2)x^(-2)+(3)x^(1)-(18)x^(-45)" how would I use split() to get the exponents? So this example would return [-2, 1, -45] . I tried to figure out the regex notation but it's pretty confusing. The closest I've come is string.split("x\\\\^\\\\(") but it doesn't fully split it how I want to.

Answer 1

Give this a try

String str = "(-2)x^(-2)+(3)x^(1)-(18)x^(-45)";
char[] chars = str.toCharArray();
List<String> exponents = new ArrayList<String>();
for(int i=0; i<chars.length; i++) {
    if(chars[i] == '^') {
        if(++i<chars.length && chars[i] == '(') {
            StringBuilder sb = new StringBuilder();
            while(++i<chars.length && chars[i] != ')') {
                sb.append(chars[i]);
            }
            exponents.add(sb.toString());
        }
    }
}

Answer 2

Try this if you need a regex based solution:

    String line = "(-2)x^(-2)+(3)x^(1)-(18)x^(-45)";         
    String pattern = ".*?\\^\\(([\\d-]+)\\)[\\+-]*";
    Pattern r = Pattern.compile(pattern,Pattern.MULTILINE);

    Matcher m = r.matcher(line);
    while (m.find()) {            
        System.out.println("Found value: " + m.group(1));            
    } 

Sample Demo at Debuggex