69. Sqrt(x)

Problem:

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.

思路：

Solution (C++):

int mySqrt(int x) {
    if (x == 0)  return 0;
    int root = 1;
    while (root) {
        if (x / root >= root && x / (root+1) < (root+1))  return root;
        ++root;
    }
    return root;
}

性能：

Runtime: 152 ms  Memory Usage: 6.1 MB

思路：

Solution (C++):

性能：

Runtime: ms  Memory Usage: MB