给定一个包含多项式项的字符串，任务是评估该多项式的导数。
什么是多项式？
多项式有两个词：-“ Poly”表示“许多”，“ nomial”表示“项”，其中包括许多项。多项式表达式是包含变量，系数和指数的表达式，它仅涉及变量的加，乘和减运算。
多项式示例
x2 + x + 1
多项式p(x)= mx ^ n的导数为-
m * n * x ^(n-1)
示例
Input: str = "2x^3 +1x^1 + 3x^2" val = 2 Output: 37 Explanation: 6x^2 + 1x^0 + 6x^1 Putting x = 2 6*4 + 1 + 6*2 = 24 + 1 + 12 = 37 Input: str = “1x^3” val = 2 Output: 12 Explanation: 1 * 3 *x^2 Putting x = 2 3 * 4 = 12
我们将用来解决上述问题的方法-
将输入作为字符串和值x
现在遍历字符串并检查数字和变量。
继续添加和遍历字符串，直到找到“ +”。
然后m * n * x ^(n-1)。
返回结果。
算法
Start Step 1-> In function long long term(string polyterm, long long val) Declare and initialize coeffStr = "” Declare i Loop For i = 0 and polyterm[i] != 'x' and i++ Call coeffStr.push_back(polyterm[i]) Set coeff = atol(coeffStr.c_str() Declare and initialize powStr = "" Loop For i = i + 2 and i != polyterm.size() and i++ powStr.push_back(polyterm[i]) Set power = atol(powStr.c_str()); Return coeff * power * pow(val, power - 1) Step 2-> In function long long value(string& str, int val) Set ans = 0 Call istringstream is(str) Declare string polyterm Loop While is >> polyterm If polyterm == "+” then, Continue Else Set ans = (ans + term(polyterm, val)) Return ans Step 3-> In function int main() Declare and initialize str = "2x^3 + 1x^1 + 3x^2" Declare and initialize val = 2 Print the value received by value(str, val) Stop
示例
#include
using namespace std;
long long term(string polyterm, long long val) {
//找到系数
string coeffStr = "";
int i;
for (i = 0; polyterm[i] != 'x'; i++)
coeffStr.push_back(polyterm[i]);
long long coeff = atol(coeffStr.c_str());
//获得幂值
string powStr = "";
for (i = i + 2; i != polyterm.size(); i++)
powStr.push_back(polyterm[i]);
long long power = atol(powStr.c_str());
//对于ax ^ n，我们返回a(n-1)x ^(n-1)
return coeff * power * pow(val, power - 1);
}
long long value(string& str, int val) {
long long ans = 0;
//使用istringstream获取令牌中的输入
istringstream is(str);
string polyterm;
while (is >> polyterm) {
//检查令牌是否等于“ +”，然后
//继续字符串
if (polyterm == "+")
continue;
//否则找到那个的导数
//特定术语
else
ans = (ans + term(polyterm, val));
}
return ans;
}
//主要功能
int main() {
string str = "2x^3 + 1x^1 + 3x^2";
int val = 2;
cout << value(str, val);
return 0;
}输出结果
37
