C++ 解法, 执行用时: 1ms, 内存消耗: 392KB, 提交时间: 2017-06-10

class Solution {
public:
    int sqrt(int x) {
        if(x <= 1)return x;
        
        int begin = 1;  
        int end   = x;  
        int middle = 0;  
        while(begin<=end) {  
            middle = (begin + end)/2;  
            //不要写成middle*middle==x，会溢出  
            if(middle==x/middle) {  
                return middle;  
            } 
            else {  
                if (middle<x/middle) {  
                    begin = middle + 1;  
                } 
                else {  
                    end = middle - 1;  
                }  
            }  
              
        }   
        //结束条件end一定<begin，所以返回end  
        return end;  
    }
};

C++ 解法, 执行用时: 2ms, 内存消耗: 320KB, 提交时间: 2021-02-02

class Solution {
public:
    /**
     * 
     * @param x int整型 
     * @return int整型
     */
    int sqrt(int x) {
          int i = 1;
        int res = 0;
        while(x >=0){
            x -= i;
            ++res;
            i += 2;
        }
        return res-1;// write code here
    }
};

C++ 解法, 执行用时: 2ms, 内存消耗: 324KB, 提交时间: 2021-03-21

class Solution {
public:
    /**
     * 
     * @param x int整型 
     * @return int整型
     */
    int sqrt(int x) {
        // write code here
        if(x==0||x==1)
            return x;
        int l=0,r=x,res=-1;
        while(l<=r){
            int mid=l+(r-l)/2;
            if((long long)mid*mid<=x){
                res=mid;
                l=mid+1;
            }else{
                r=mid-1;
            }
        }
        return res;
    }
};

C++ 解法, 执行用时: 2ms, 内存消耗: 328KB, 提交时间: 2021-06-05

class Solution {
public:
    /**
     * 
     * @param x int整型 
     * @return int整型
     */
    int sqrt(int x) {
        if (x<2)
        {
            return x;
        }
        int left=1;
        int right=x/2;
        int mid=1;
        while (left<=right)
        {
            mid=(left+right)/2;
            if (x/mid==mid)
            {
                return mid;
            }
            else if (x/mid<mid)
            {
                right=mid-1;
            }
            else{
                left=mid+1;
            }
        }
        return right;
    }
};

C++ 解法, 执行用时: 2ms, 内存消耗: 328KB, 提交时间: 2021-05-17

class Solution {
public:
    /**
     * 
     * @param x int整型 
     * @return int整型
     */
    int sqrt(int x) {
        // write code here
        if(x<0)
            return -1;
        int i = 1;
        int j = x;
        int mid;
        while(i<=j){
            mid = (i+j)>>1;
            if(mid*mid==x)
                return mid;
            if(mid>x/mid)
                j = mid-1;
            else
                i = mid+1;
        }
        return j;
    }
};