comefrom: <qiyuangong>367_Valid_Perfect_Square_1.java
code: public boolean isPerfectSquare(int num) {
          int low = 1;
          int high = num;
          while (low <= high) {
              long mid = (low + high) >>> 1;
              if (mid * mid == num) {
                  return true;
              } else if (mid * mid < num) {
                  low = (int) mid + 1;
              } else {
                  high = (int) mid - 1;
              }
          }
          return false;
      }
masked: public boolean var_0 ( int var_1 ) {
    int var_2 = 1 ;
    int var_3 = var_1 ;
    while ( var_2 <= var_3 ) {
      long var_4 = ( var_2 + var_3 ) >>> 1 ;
      if ( var_4 * var_4 == var_1 ) {
        return true ;
      }
      else if ( var_4 * var_4 < var_1 ) {
        var_2 = ( int ) var_4 + 1 ;
      }
      else {
        var_3 = ( int ) var_4 - 1 ;
      }
    }
    return false ;
  }
  