leetcode ValidPerfectSquare
z
 2019-04-09 10:36:27   
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public class ValidPerfectSquare {
  /*
      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
      Output: true
      Example 2:

      Input: 14
      Output: false
   */
  public boolean isPerfectSquare(int num) {
    // 时间代价太高，可以使用二分搜索
    int i=num/2;
    if (num < 0){
      return false;
    }
    for (int n = 0; n<=i; n++){
      if (n*n == num)
        return true;
    }
    return false;

  }
}