@interface StringPermutations : NSObject  - (void)permuteString:(NSString *)inputString;  @end  #import "StringPermutations.h"  @implementation StringPermutations  - (void)permuteString:(NSString *)inputString {    NSString *chars = inputString;    NSArray *charArray = [chars componentsSeparatedByString: @""];    if (charArray.count <= 1) {      NSLog(@"排列结果：%@", inputString);      return;    }    NSMutableString *result = [NSMutableString string];    void permute(NSArray *array, NSUInteger index, NSString *currentString,               NSMutableArray *used, NSString *resultString) {      if (index == array.count) {        [resultString appendFormat: @"'%@'", currentString];        [result appendString: resultString];        [resultString reset];        return;      }      for (NSUInteger i = 0; i < array.count; i++) {        if (![(NSNumber *)[array objectAtIndex:i] boolValue]) {          [permute array: array, index: i+1, currentString: [currentString appendFormat: @"'%c'",                     [array[i] characterAtIndex: 0]], used: used, resultString: resultString);        }      }      [resultString reset];    }    NSMutableArray *used = [NSMutableArray array];    [permute charArray, 0, @"", used, result];    for (NSString *str in [result componentsSeparatedByString: @"\n"]) {      NSLog(@"排列结果：%@", str);    }  }  @end