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nCr mod p c++

Akshat Shah 5-Year IDD Mathematical Sciences answered on August 8, 2022 Popularity 6/10 Helpfulness 4/10

answer nCr mod p c++

nCr mod p c++

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// A Dynamic Programming based solution to compute nCr % p
#include <bits/stdc++.h>
using namespace std;
 
// Returns nCr % p
int nCrModp(int n, int r, int p)
{
    // Optimization for the cases when r is large
    if (r > n - r)
        r = n - r;
 
    // The array C is going to store last row of
    // pascal triangle at the end. And last entry
    // of last row is nCr
    int C[r + 1];
    memset(C, 0, sizeof(C));
 
    C[0] = 1; // Top row of Pascal Triangle
 
    // One by constructs remaining rows of Pascal
    // Triangle from top to bottom
    for (int i = 1; i <= n; i++) {
 
        // Fill entries of current row using previous
        // row values
        for (int j = min(i, r); j > 0; j--)
 
            // nCj = (n-1)Cj + (n-1)C(j-1);
            C[j] = (C[j] + C[j - 1]) % p;
    }
    return C[r];
}
 
// Driver program
int main()
{
    int n = 10, r = 2, p = 13;
    cout << "Value of nCr % p is " << nCrModp(n, r, p);
    return 0;
}

Popularity 6/10 Helpfulness 4/10 Language cpp

Source: www.geeksforgeeks.org

Tags: c++ mod ncr

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