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.

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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;
    }
};