<awangdev>367. Valid Perfect Square_1.java
public boolean isPerfectSquare(int num) {
        long start = 0, end = num;
        while (start <= end) {
            long mid = start + (end - start) / 2;
            long sqrt = mid * mid;
            if (sqrt == num) return true;
            else if (sqrt < num) start = mid + 1;
            else end = mid - 1;
        }
        return false;
    }
public boolean var_0 ( int var_1 ) {
  long var_3 = 0 , var_4 = var_1 ;
  while ( var_3 <= var_4 ) {
    long var_6 = var_3 + ( var_4 - var_3 ) / 2 ;
    long var_7 = var_6 * var_6 ;
    if ( var_7 == var_1 ) return true ;
    else if ( var_7 < var_1 ) var_3 = var_6 + 1 ;
    else var_4 = var_6 - 1 ;
  }
  return false ;
}
