[LeetCode-69] Sqrt(x)（求解平方根）

Implement 

int sqrt(int x)

.

Compute and return the square root of x.

这道题一看到函数的定义int sqrt(int x)都是int就高兴了，直接二分吧。但是要注意，即使用long long都越界，还要用unsigned long long。最后返回值还要再检查一下。

http://blog.csdn.net/doc_sgl/article/details/12404971

int mySqrt(int x)
{
// Start typing your C/C++ solution below
// DO NOT write int main() function

unsigned long long begin = 0;
unsigned long long end = (x+1)/2;
unsigned long long mid;
unsigned long long tmp;

while(begin < end) {
mid = begin + (end-begin)/2;
tmp = mid*mid;
if(tmp==x)
return mid;
else if(tmp<x)
begin = mid+1;
else
end = mid-1;
}

tmp = end*end;

if(tmp > x)
return end-1;
else
return end;

}



如果是double 或者 float 类型时

需要使用---->牛顿迭代法