題目描述：

    Implement int sqrt(int x).
    Compute and return the square root of x.
    x is guaranteed to be a non-negative integer.

例子：

Input: 4
Output: 2

Input: 8
Output: 2
Explanation: The square root of 8 is 2.82842..., and since we want to return an integer, the decimal part will be truncated.

分析：
    題意：給定一個非負整型數x，返回x的算術平方根。

程式碼：

#include <bits/stdc++.h>

using namespace std;

#define LL long long

class Solution {
public:
    int mySqrt(int x) {
		// Exceptional Case: 
        if(x <= 1){
			return x;
		}
		int left = 1, right = x;
		while(left <= right){
			int mid = left + (right - left) / 2;
			if((LL)mid * (LL)mid == (LL)x){
				return mid;
			}
			else if((LL)mid * (LL)mid > (LL)x){
				right = mid - 1;
			}
			else if((LL)mid * (LL)mid < (LL)x){
				left = mid + 1;
			}
		}
		return right;
    }
};