Explanation and usage of sqrt() function

Hello everyone , I meet you again , I'm your friend, Quan Jun .

sqrt() Function is a function we often use . Now I will introduce its usage and usage specification in detail

Required header file

#include<math.h>

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The function prototype

double sqrt(double x);

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effect : sqrt() Used to find the square root of a given value

Common usage errors Output 36 The root of the root

Ignored sqrt() The return value of the function is double type . Make a mistake

The solution is as follows :

Common use sqrt() The standard writing of functions for example : We have to judge whether a number is a prime number , Just judge 2 ~ n Square root If there is a number that can be divided by an integer The wrong way to write :

bool find(int n)
{ 
   
	for(int i=2;i<=sqrt(n);i++)
	{ 
   
		if(n%i==0)
			return false;
	}
	return true;
}

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The way it's written is , Actually, it is not recommended to write in this way . Although I often write like this . But in the process of doing questions , Just because of this writing program appeared bug. I'll use the following safe way of writing Correct writing :

bool find(int n)
{ 
   
	int sql=(int)sqrt(1.0*n);//1.0*n Is the purpose of   Implicit conversion to floating point number , Cast to integer after root  
	for(int i=2;i<=sql;i++)
	{ 
   
		if(n%i==0)
			return false;
	}
	return true;
}

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