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leetcode【69】Sqrt(x)

程序员文章站 2022-03-19 11:57:02
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问题描述:

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.

源码:

最简单的方法

库函数,不合规矩。

leetcode【69】Sqrt(x)

class Solution {
public:
    int mySqrt(int x) {
        return int(sqrt(x));
    }
};

暴力低效法:

leetcode【69】Sqrt(x)

class Solution {
public:
    int mySqrt(int x) {
        unsigned int i=0;
        for(i=0; i<=x/2; i++){
            if(i*i<=x && (i+1)*(i+1)>x)
                break;
        }
        return i;
    }
};

分治法:

大佬的方法,分治法,恍然大悟。

leetcode【69】Sqrt(x)

class Solution {
public:
    int mySqrt(int x) {
        if(x==0)    return 0;
        unsigned int left=1, right=x/2+1, mid=0;
        while(left<=right){
            mid = (left+right)/2;
            if(mid<x/mid)   left = mid+1;
            else if(mid>x/mid)  right = mid-1;
            else{
                return mid;
            }
        }
        return right;
        // return 0;
    }
};