LeetCode 69 — Sqrt(x)（C++ Java Python）

题目：http://oj.leetcode.com/problems/sqrtx/

Implement 

int
sqrt(int x)

.

Compute and return the square root of x.

题目翻译：

实现int sqrt(int x)。

计算并返回x的平方根。

分析：

        二分查找。注意结果不是整数时应返回整数部分。

C++实现：

class Solution {
public:
int sqrt(int x) {
// Note: The Solution object is instantiated only once and is reused by each test case.
if(x < 2)
{
return x;
}

int left = 1;
int right = x / 2;
int mid = 0;
int lastMid = 0;

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

return lastMid;
}
};

Java实现：

public class Solution {
public int sqrt(int x) {
// Note: The Solution object is instantiated only once and is reused by each test case.
if (x < 2) {
return x;
}

int low = 1;
int high = x / 2;
int mid = 0;
int lastMid = 0;

while (low <= high) {
mid = (low + high) / 2;
if (x / mid > mid) {
low = mid + 1;
lastMid = mid;
} else if (x / mid < mid) {
high = mid - 1;
} else {
return mid;
}
}

return lastMid;
}
}

Python实现：

class Solution:
# @param x, an integer
# @return an integer
def sqrt(self, x):
if x < 2:
return x

left = 1
right = x / 2

while left <= right:
mid = (left + right) / 2
if(x > mid * mid):
left = mid + 1
lastMid = mid
elif(x < mid * mid):
right = mid - 1
else:
return mid

return lastMid

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