69.x的平方根 367.完全有效的平方数
题目:69. x 的平方根 - 力扣(L69eetCode)
经典平方根问题,用二分法慢慢逼近找开方值,注意mid*mid要用long long值,不然会溢出
class Solution {
public:
int mySqrt(int x) {
int left = 0; int right = x;
int ans = -1;
while( left <= right )
{
int mid = left + (right - left)/2;//防止溢出
if((long long) mid * mid <= x)
{
ans = mid;
left = mid + 1;
}
else
right = mid -1;
}
return ans;//保留小的
}
};
此题的推广367. 有效的完全平方数 - 力扣(LeetCode)
只要把想等的情况单拧出来就可以了
class Solution {
public:
bool isPerfectSquare(int num) {
int left = 0; int right = num;
while( left <= right )
{
int mid = left + (right - left)/2;//防止溢出
if((long long) mid * mid == num)
return true;
if((long long) mid * mid < num)
left = mid + 1;
else
right = mid -1;
}
return false;
}
};
原文地址:https://blog.csdn.net/zengxuan151168/article/details/142746538
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