Given a positive integer num, write a function which returns True if num is a perfect square else False.
Note: Do not use any built-in library function such as sqrt.
Example 1:
Input: 16 Returns: True
Example 2:
Input: 14 Returns: False
class Solution {
public boolean isPerfectSquare(int num) {
if(num ==1) return true;
int start = 1;
int end = num;
while(start<end){
int mid = start + (end-start)/2;
if(mid*mid == num){
return true;
}
if(mid < num/mid){
start = mid+1;
}
else{
end = mid;
}
}
return false;
}
}
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原文作者：Jake Tao，来源：「367. Valid Perfect Square」
