在一个数组中 找和给定数的下标

 - (void)viewDidLoad {
    [super viewDidLoad];
    NSArray *arr = @[@"1",@"3",@"5",@"7",@"11"];
    
    NSArray *indexArr = [self getIndexWithSum:12 InArr:arr];
    
    if (indexArr.count>0) {
        NSLog(@"-->%@",indexArr);
    }else{
        NSLog(@"数组中没有要找的数据");
    }
    
}


-(NSArray *)getIndexWithSum:(NSInteger )sum InArr:(NSArray *)arr{
    
    NSMutableArray *indexArr = [NSMutableArray array];
    NSMutableDictionary *indexDic = [NSMutableDictionary dictionary];
    
    for (int i = 0 ; i < arr.count; i++) {
        
        NSInteger otherNum = sum - [arr[i] integerValue];
        
        if ([[indexDic allKeys] containsObject:arr[i]]) {
            NSLog(@"before index--->%@",[indexDic objectForKey:arr[i]]);
            NSLog(@"after index --->%d",i);
            [indexArr addObject:[indexDic objectForKey:arr[i]]];
            [indexArr addObject:@(i)];
            break;
        }else{
            [indexDic setValue:[NSString stringWithFormat:@"%d",i] forKey:[NSString stringWithFormat:@"%ld",otherNum]];
        }
        
        
    }
    
    
    return indexArr;
}