LeetCode:Sqrt(x)

Sqrt(x)

Total Accepted: 94989 Total
Submissions: 373552 Difficulty: Medium

Implement 

int sqrt(int x)

.
Compute and return the square root of x.

Subscribe to see which companies asked this question

Hide Tags
 Binary Search Math

Hide Similar Problems
 (M) Pow(x, n)

思路：二分查找。

如：x = 10

1 2 3 4 5 6 7 8 9 10

设：left = 1,right = 10，则 mid = (1+10)/2 = 5

由于mid * mid > x * x，则right = mid;这时，left = 1,right = 5,mid = (1+5)/2 = 3;

由于mid * mid <= x * x，则left = mid;这时，left = 3,right = 5,mid = (3+5)/2 = 4;

由于mid * mid > x * x，则right = mid;这时，left = 3,right = 4,mid = (3+4)/2 = 3;

由于 left + 1 == right,break;

返回结果：left = 3;

c++ code:

class Solution {
public:
int mySqrt(int x) {
if(x <= 1) return x;

int left = 1,right = x;

while(left + 1 < right) {
int mid = left + (right-left)/2;
if(mid <= x/mid)
left = mid;
else
right = mid;
}
return left;
}
};