时间复杂度：O(n log n)
代码：
- (NSArray *)mergeSort:(NSArray *)array {
NSMutableArray *tmpArray = [[NSMutableArrayalloc] init];
for(inti =0; i < array.count; i++) {
NSMutableArray *subArray = [[NSMutableArrayalloc] init];
[subArray addObject:array[i]];
[tmpArray addObject:subArray];
}
while(tmpArray.count != 1) {
NSUIntegerj = 0;
while(j < tmpArray.count-1) {
tmpArray[j] = [self mergeSortedArray:tmpArray[j] secondArray:tmpArray[j +1]];
[tmpArray removeObjectAtIndex:j +1];
j ++;
}
}
returnt mpArray.firstObject;
}
- (NSArray *)mergeSortedArray:(NSArray *)firstArray secondArray:(NSArray *)secondArray {
NSMutableArray *resultArray = [[NSMutableArrayalloc] init];
NSUInteger firstIndex =0;
NSUInteger secondIndex =0;
while(firstIndex < firstArray.count && secondIndex < secondArray.count) {
if(firstArray[firstIndex] < secondArray[secondIndex]) {
[resultArray addObject:firstArray[firstIndex]];
firstIndex ++;
}else{
[resultArray addObject:secondArray[secondIndex]];
secondIndex ++;
}
}
while(firstIndex < firstArray.count) {
[resultArray addObject:firstArray[firstIndex]];
firstIndex ++;
}
while(secondIndex < secondArray.count) {
[resultArray addObject:secondArray[secondIndex]];
secondIndex ++;
}
return resultArray;
}