【LeetCode 0069】【二分查找】求平方根

69. Sqrt(x)

Given a non-negative integer x, return the square root of x rounded down to the nearest integer. The returned integer should be non-negative as well.

You must not use any built-in exponent function or operator.

• For example, do not use pow(x, 0.5) in c++ or x ** 0.5 in python.

Example 1:

**Input:** x = 4
**Output:** 2
**Explanation:** The square root of 4 is 2, so we return 2.

Example 2:

**Input:** x = 8
**Output:** 2
**Explanation:** The square root of 8 is 2.82842..., and since we round it down to the nearest integer, 2 is returned.

Constraints:

• 0 <= x <= 2^31 - 1

JavaScript Solution

/**
 * @param {number} x
 * @return {number}
 */
var mySqrt = function(x) {
    /*
    let ans = 0;
    while(x  >= (ans+1)**2){
        ans++;
    }
    return ans
    */
    let f = 0
    for(let s = x; s > 0; s = ~~(s/2)){
        while((f+s)*(f+s)<=x)f+=s
    }
    return f
};