Question

How to get the square root rounded down to the nearest integer of a positive integer in C++

Answer 1

#include <iostream>

int mySqrt(int n) {
	if (n == 0 || n == 1) {
		return n;
	}

	int start = 1;
	int end = n;

	while (start <= end) {
		int mid = start + (end - start) / 2;

		if (static_cast<long>(mid) * mid > static_cast<long>(n)) {
			end = mid - 1;
		}
		else if (mid * mid == n) {
			return mid;
		}
		else {
			start = mid + 1;
		}
	}

	return end;
}

int main()
{
	std::cout << mySqrt(240000) << std::endl; // 489.897
}

 
 
/*
run:
 
489
 
*/

 

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