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Error
Given two integers n and r, find nCr. Since the answer may be very large, calculate the answer modulo 109+7.
Example 1:
Input: n = 3, r = 2
Output: 3
Explaination: 3C2 = 3.
Example 2:
Input: n = 2, r = 4 Output: 0 Explaination: r is greater than n.
Your Task:
You do not need to take input or print anything. Your task is to complete the function nCr() which takes n and r as input parameters and returns nCr modulo 109+7..
Expected Time Complexity: O(n*r)
Expected Auxiliary Space: O(r)
Constraints:
1 ≤ n ≤ 1000
1 ≤ r ≤ 800
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