字符在NSString中的位置與NSArray - 性能/效率

Question

有誰知道在NSString或相同字符的NSArray中查找字符的速度更有效嗎？

我想知道哪個具有最好和最有效的算法來找到正確的值。

我真的很想找到字母在字母表中的位置。例如在字母表中找到「E」的位置@"ABCDE....XYZ"或[NSArray arrayWithObjects:@"A",@"B",@"C",@"D",@"E",...,@"X",@"Y",@"Z"];

哪個更適合搜索？ NSString或NSArray？

Answer 1

如果只是A-Z：

NSString *string = @"A"; 
int position = (int)[string characterAtIndex:0]-64; 
NSLog(@"%d", position); 

只是出於好奇：

NSString *alphabetString = @"ABCDEFGHIJKLMNOPQRSTUVWXYZ"; 
NSMutableArray *alphabetArray = [NSMutableArray array]; 
for(int pos = 0; pos < [alphabetString length]; pos++) { 

    [alphabetArray addObject:[alphabetString substringWithRange:NSMakeRange(pos, 1)]]; 
} 

NSString *check = @"A"; 

// check with rangeOfString 
NSDate *start = [NSDate date]; 
for(int i = 0; i < 1000000; i++) { 

    int position = [alphabetString rangeOfString:check].location + 1; 
} 
NSDate *end = [NSDate date]; 
NSLog(@"STRING | time needed: %f", [end timeIntervalSinceDate:start]); 

// check with indexOfObject 
start = [NSDate date]; 
for(int i = 0; i < 1000000; i++) { 

    int position = [alphabetArray indexOfObject:check] + 1; 
} 
end = [NSDate date]; 
NSLog(@"ARRAY | time needed: %f", [end timeIntervalSinceDate:start]); 

// check with ASCII position 
start = [NSDate date]; 
for(int i = 0; i < 1000000; i++) { 

    int position = (int)[check characterAtIndex:0]-64; 
} 
end = [NSDate date]; 
NSLog(@"ASCII | time needed: %f", [end timeIntervalSinceDate:start]); 

控制檯：

STRING | time needed: 0.156067 
ARRAY | time needed: 0.213297 
ASCII | time needed: 0.017055