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// Source : https://oj.leetcode.com/problems/sqrtx/

// Author : Hao Chen

// Date : 2014-08-26

/**********************************************************************************

*

* Implement int sqrt(int x).

*

* Compute and return the square root of x.

*

**********************************************************************************/

#include <stdlib.h>

#include <iostream>

using namespace std;

int sqrt(int x) {

if (x <=0 ) return 0;

//the sqrt is not greater than x/2+1

int e = x/2+1;

int s = 0;

// binary search

while ( s <= e ) {

int mid = s + (e-s)/2;

long long sq = (long long)mid*(long long)mid;

if (sq == x ) return mid;

if (sq < x) {

s = mid + 1;

}else {

e = mid - 1;

}

}

return e;

}

// http://en.wikipedia.org/wiki/Newton%27s_method

int sqrt_nt(int x) {

if (x == 0) return 0;

double last = 0;

double res = 1;

while (res != last)

{

last = res;

res = (res + x / res) / 2;

}

return int(res);

}

int main(int argc, char**argv)

{

int n = 2;

if( argc > 1 ){

n = atoi(argv[1]);

}

cout << "sqrt(" << n << ") = " << sqrt(n) << endl;

return 0;

}