LeetCode第367題_Valid Perfect Square

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

注意
-2 回傳 false
-1 回傳 false
0  回傳 false
1 回傳 true
2 回傳  false
4 回傳 true
16 回傳 true



然後一樣小心over flow 所以迴圈尋訪不用int 改用long
較保險

CODE

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/* * To change this license header, choose License Headers in Project Properties. * To change this template file, choose Tools | Templates * and open the template in the editor. */ package leetcode367_validperfectsquare; import java.io.BufferedReader; import java.io.IOException; import java.io.InputStreamReader; /** * * @author chous */ public class LeetCode367_ValidPerfectSquare { /** * @param args the command line arguments */ public static void main(String[] args) throws IOException { // TODO code application logic here BufferedReader input; input = new BufferedReader(new InputStreamReader(System.in)); System.out.println("Input"); String strInput = input.readLine(); int numInput = Integer.parseInt(strInput); System.out.println(isPerfectSquare(numInput)); } public static boolean isPerfectSquare(int num){ if(num<=0) return false; if(num==1) return true; for(long i=1;i<=num;i++){ if(i*i == num){ return true; } } return false; } }