现有一个文件input.txt，内容如下： N=x(x为从2到100的随机数字) 请编写一段c++代码，定义一个int型变量n，将“N=”后面的数字赋值给n

Sure! Here's a C++ code snippet that reads the input.txt file, extracts the value after "N=", and assigns it to an integer variable n:

#include <iostream>
#include <fstream>
#include <string>

int main() {
    std::ifstream inputFile("input.txt");
    std::string line;

    if (inputFile.is_open()) {
        while (std::getline(inputFile, line)) {
            size_t found = line.find("N=");
            if (found != std::string::npos) {
                int n = std::stoi(line.substr(found + 2));
                std::cout << "n = " << n << std::endl;
                break;
            }
        }
        inputFile.close();
    } else {
        std::cout << "Unable to open input.txt file" << std::endl;
    }

    return 0;
}

This code opens the input.txt file, reads it line by line, and searches for a line containing "N=". If found, it extracts the value after "N=" using substr() function and converts it to an integer using stoi() function. Finally, it assigns the value to the variable n and prints it.