有一个来自用户的字符串输入。这是一个多项式。如何在不使用数组的情况下导出此polinom？
ınput=3x^4+5x^45-2+77x^100
输出必须是12x^3 + 225x^44 + 7700x^99
我怎么知道多项式中有多少个x语句？
我的代码是：
String katsayi = polinom.substring(0, polinom.indexOf("x"));
String us = polinom.substring(a + 1);
int katSayi = Integer.parseInt(katsayi);
int uS = Integer.parseInt(us);
katSayi = katSayi * uS;
uS = uS - 1;
katsayi = Integer.toString(katSayi);
us = Integer.toString(uS);
yeniPolinom = katsayi + "x^" + us;
System.out.println(yeniPolinom);
public static void main(String[] args) throws IOException {
String polynomial = "3x^4+5x^45-2+77x^100";
int lastNumber = 0;
int temp = 0;
String output = "";
for(int i = 0; i < polynomial.length() - 1; i++)
{
if(polynomial.charAt(i) == 'x')
{
int counter = i + 1;
int a = 0;
int b = 0;
String tempString1 = "";
String tempString2 = "";
String number = "";
while((polynomial.charAt(counter) != '0') && (polynomial.charAt(counter) != '1') && (polynomial.charAt(counter) != '2') && (polynomial.charAt(counter) != '3') && (polynomial.charAt(counter) != '4') && (polynomial.charAt(counter) != '5') && (polynomial.charAt(counter) != '6') && (polynomial.charAt(counter) != '7') && (polynomial.charAt(counter) != '8') && (polynomial.charAt(counter) != '9'))
{
tempString1 += polynomial.charAt(counter);
counter++;
}
while((counter < polynomial.length()) && ((polynomial.charAt(counter) == '0') || (polynomial.charAt(counter) == '1') || (polynomial.charAt(counter) == '2') || (polynomial.charAt(counter) == '3') || (polynomial.charAt(counter) == '4') || (polynomial.charAt(counter) == '5') || (polynomial.charAt(counter) == '6') || (polynomial.charAt(counter) == '7') || (polynomial.charAt(counter) == '8') || (polynomial.charAt(counter) == '9')))
{
number += polynomial.charAt(counter);
counter++;
}
a = Integer.parseInt(number);
temp = counter - 1;
counter = i - 1;
number = "";
while((polynomial.charAt(counter) != '0') && (polynomial.charAt(counter) != '1') && (polynomial.charAt(counter) != '2') && (polynomial.charAt(counter) != '3') && (polynomial.charAt(counter) != '4') && (polynomial.charAt(counter) != '5') && (polynomial.charAt(counter) != '6') && (polynomial.charAt(counter) != '7') && (polynomial.charAt(counter) != '8') && (polynomial.charAt(counter) != '9'))
{
tempString2 = polynomial.charAt(counter) + tempString2;
counter--;
}
while((counter >= 0) && ((polynomial.charAt(counter) == '0') || (polynomial.charAt(counter) == '1') || (polynomial.charAt(counter) == '2') || (polynomial.charAt(counter) == '3') || (polynomial.charAt(counter) == '4') || (polynomial.charAt(counter) == '5') || (polynomial.charAt(counter) == '6') || (polynomial.charAt(counter) == '7') || (polynomial.charAt(counter) == '8') || (polynomial.charAt(counter) == '9')))
{
number = polynomial.charAt(counter) + number;
counter--;
}
b = Integer.parseInt(number);
for(int j = lastNumber; j <= counter; j++)
{
output += polynomial.charAt(j);
}
output += "" + (a * b) + "x^" + (a - 1);
lastNumber = temp + 1;
i = temp;
}
}
System.out.println(output);
}
输出：
12x^3+225x^44-2+7700x^99
解析一个看起来像多项式的字符串可能非常乏味，因为有数百种方法可以写下同一个多项式。然而，如果我们坚持格式ax^n，你可以看看这个答案来提取多项式的系数：https://stackoverflow.com/a/13415745/1743880.
考虑使用derivative方法来创建一个Polynom类。
使用regex查找格式为[number1]x^[number2]的零件，然后用[num1]*[num2]x^[num2 - 1]替换这些零件如何？下面是一个基于所找到的值动态创建替换零件的示例。
String input = "3x^4+5x^45-2+77x^100";
Pattern p = Pattern.compile("(\d+)x\^(\d+)");
// ^^^^ ^^^^
// group1 group2
Matcher m = p.matcher(input);
StringBuffer sb = new StringBuffer();
while (m.find()) {
int a = Integer.parseInt(m.group(1));
int n = Integer.parseInt(m.group(2));
if (n != 0)
m.appendReplacement(sb, (a * n) + "x^" + (n - 1));
else
m.appendReplacement(sb, "0");
}
m.appendTail(sb);
String output = sb.toString();
System.out.println(output);
输出：12x^3+225x^44-2+7700x^99
请注意，此解决方案非常有限。它假设所有部分都将以ax^n的形式编写，因此对于像x^2而不是1x^2或-1而不是-1x^0这样的数据，它将无法正确工作。我还假设n不会是负数。