我一直在尝试关于黑客等级的问题,其中考虑了字符串的所有子字符串的加法。 这样做,我们的答案超出了NSInteger,NSUInteger,长,非常长,两倍的限制。
所以在这种情况下,我尝试了
- (NSDecimalNumber *) substrings:(NSString *)n {
NSCharacterSet* notDigits = [[NSCharacterSet decimalDigitCharacterSet] invertedSet];
if ([n rangeOfCharacterFromSet:notDigits].location == NSNotFound) {
NSNumberFormatter *f = [[NSNumberFormatter alloc] init];
f.numberStyle = NSNumberFormatterNoStyle;
NSDecimalNumber *sum = [NSDecimalNumber decimalNumberWithString:@"0"];
NSMutableArray *arr = [[NSMutableArray alloc] init];
for (NSInteger i = 0; i<n.length; i++) {
for (NSInteger j = 1; j<=n.length-i; j++) {
NSString *stringInRange = [n substringWithRange:NSMakeRange(i, j)];
[arr addObject:stringInRange];
NSDecimalNumber *myNumber1 = [NSDecimalNumber decimalNumberWithString:stringInRange];
sum = [sum decimalNumberByAdding:myNumber1];
}
}
return sum;
} else {
return nil;
}
}
但是,我仍然得到加法的错误答案。我想知道在这种情况下,测试用例包含的值比限制值大得多,我们应该使用哪种API来执行算术运算?
我尝试过的方法是否正确?
答案 0 :(得分:0)
如果需要在Objective-C中使用大整数值进行运算,则可以使用JKBigInteger。例如,您可以将2个大整数相乘,然后使用JKBigInteger将结果转换为NSString
。在这里,您可以了解如何使用该库:
JKBigInteger *bigInteger1 = [[JKBigInteger alloc] initWithString:@"2"];
JKBigInteger *bigInteger2 = [[JKBigInteger alloc] initWithString:@"3"];
JKBigInteger* bigInteger3 = [bigInteger1 add:bigInteger2];
NSLog(@"%@", [bigInteger3 stringValue]); // output is 5
我想您可以使用此功能获得所需的值:
-(JKBigInteger*)sumOfSubValues:(JKBigInteger*)value {
JKBigInteger* currentValue = [[JKBigInteger alloc] initWithString:value.stringValue];
JKBigInteger* result = [[JKBigInteger alloc] initWithString:currentValue.stringValue];
NSUInteger digitsCount = currentValue.stringValue.length - 1;
JKBigInteger* const tenValue = [[JKBigInteger alloc] initWithString:@"10"];
while (digitsCount != 0) {
JKBigInteger* const firstDigit = [[JKBigInteger alloc] initWithString:[currentValue.stringValue substringToIndex:1]];
JKBigInteger* const firstDigitPowerBase = [tenValue pow:(unsigned int)digitsCount];
JKBigInteger* const firstDigitPower = [firstDigit multiply:firstDigitPowerBase];
JKBigInteger* const diff = [currentValue subtract:firstDigitPower];
currentValue = diff;
digitsCount--;
result = [result add:currentValue];
}
return result;
}
您可以使用以下代码段对其进行测试:
JKBigInteger* result = [self sumOfSubValues:[[JKBigInteger alloc] initWithString:@"1234"]];
NSLog(@"%@", result.stringValue); // output is "1506" (1234 + 234 + 34 + 4)