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Leetcode069-sqrt(x)

Posted on Edited on In Views: Valine:
Solution Report of LeetCode Acceptted

Description

Implement

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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

Example 1:

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Input: 4
Output: 2

Example 2:
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Input: 8
Output: 2
Explanation: The square root of 8 is 2.82842..., and since 
             the decimal part is truncated, 2 is returned.

Solution

Newton’s method: https://blog.csdn.net/chenrenxiang/article/details/78286599

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class Solution {
    public int mySqrt(int x) {

//         Method 1 (Good to solve): Binary Search        
//         if (x == 0) return 0;
//         int left  = 1;
//         int right = Integer.MAX_VALUE;
        
//         while(left <= right){
//             int mid = left + (right - left)/2;
//             if (mid == x/mid) return mid;
//             else if (mid < x/mid) left = mid + 1;
//             else if (mid > x/mid) right = mid - 1;
//         }
//         return right;
        
        // Newton's method
        long r = x;
        while (r*r > x){
            r = (r + x/r)/2;
        }
        return (int)r;
    }
}