Thread: bigint modpow

  1. #1
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    bigint modpow

    hello, im searching a function in c for modular exponentiation modpow using bigint.
    i just find for c#, anyone can help?

  2. #2
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    By "bigint" you mean multiple precision arithmetic integer types?
    Try libgmp.

  3. #3
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    i need this function

    Code:
    int power(int x, int exp, int n) 
    { 
        int res = 1;      // Initialize result 
      
        x = x % n;  // Update x if it is more than or  
                    // equal to p 
      
        while (exp > 0) 
        { 
            // If y is odd, multiply x with result 
            if (exp & 1) 
                res = (res*x) % n; 
      
            // y must be even now 
            exp = exp>>1; // y = y/2 
            x = (x*x) % n;   
        } 
        return res; 
    }
    but whit type BIGINT instead int

  4. #4
    C++ Witch laserlight's Avatar
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    There is no such built-in type named BIGINT. Refer to flp1969's post #2 for a library that can help.
    Quote Originally Posted by Bjarne Stroustrup (2000-10-14)
    I get maybe two dozen requests for help with some sort of programming or design problem every day. Most have more sense than to send me hundreds of lines of code. If they do, I ask them to find the smallest example that exhibits the problem and send me that. Mostly, they then find the error themselves. "Finding the smallest program that demonstrates the error" is a powerful debugging tool.
    Look up a C++ Reference and learn How To Ask Questions The Smart Way

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