Sqrt(x)

Description

Implement intsqrt(int x).

Compute and return the square root ofx.

Example

sqrt(3) = 1

sqrt(4) = 2

sqrt(5) = 2

sqrt(10) = 3

Challenge

O(log(x))

Related problems

Sqrt(x) II

Medium Pow(x, n)

Easy First Position of Target

Implementation

Link: http://lintcode.com/en/problem/sqrtx/

class Solution {
public:
    /**
     * @param x: An integer
     * @return: The sqrt of x
     */
    int sqrt(int x) {
        // write your code here
        // Note: 
        if (x <= 1 ) {
            return x;
        }
        int start = 1;
        int end = x/2;
        while (start + 1 < end) {
            int mid = start + (end -start ) /2;
            if(mid  == x / mid) {
                return mid;
            } else if (mid < (x /mid)) {
                start = mid;
            } else {
                end = mid;
            }
        }

        return start;
    }

    int sqrtVer2(int x) {
        // write your code here
        if(x <= 1) return x;

        long start = 0, end = x / 2;
        while(start + 1 < end) {
            long mid = start + (end - start) / 2;
            if(mid * mid == x) {
                return mid;
            } else if(mid * mid < x) {
                start = mid;
            } else {
                end = mid;
            }
        }
        return start;
    }
};