Objective-C 字典怎么按值比较

[RF.Blue]

我有一系列字典， 格式都是一样的，键相同，值不同，如下：

A = {'a' = '1', 'b' = '2', ...}
B = {'a' = '1.1', 'b' = '2.1', ...}
.
.
.
N = {'a' = '100.1', 'b' = '200.1', ...}

上面的键的值都是随机的

现在有一个变量 'a' = '10‘， 我怎么快速找出所有字典里的键 'a'值和 ’10’最接近那个字典？？

[不担心]

nsdictionary *nearDict =nil;
cgfloat min=-1;
nsarray *ar = @[A,B,….N];
for (int i=0;i<ar.count,i++)
{
	nsidctionary *dict = ar[i];
	if ([dict valueForkey:@"a"] != nil
	{
		tmp = [[dict valueForkey:@"a"] floatValue];
		cgflot diff = abs(tmp-10);
		if (min==-1) 
		{
			min = diff;
		} else
		{
			if (min>diff)
			{
				nearDict = dict;
				min = diff;
			}
		}
	}	
}