LeetCode [69] Sqrt(x)

Implement int sqrt(int x).

Compute and return the square root of x, where x is guaranteed to be a non-negative integer.

Since the return type is an integer, the decimal digits are truncated and only the integer part of the result is returned.

Example 1:

Input: 4
Output: 2

Example 2:

Input: 8
Output: 2
Explanation: The square root of 8 is 2.82842..., and since 
             the decimal part is truncated, 2 is returned.

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typedef unsigned long long ull; class Solution { public: int mySqrt(int x) { int l = 0, r = x; ull m=0; while(l<=r){ m = (l+r)/2; if(m*m<=(ull)x && (m==r||(m+1)*(m+1)>(ull)x)) break; if(m*m<x) l = m+1; else r = m-1; } return m; } };