Replace all occurences of a string from a string a

问题:

I have a string array like:

 string [] items = {"one","two","three","one","two","one"};

I would like to replace all ones with zero at once. Then items should be:

{"zero","two","three","zero","two","zero"};

I found one solution How do I replace an item in a string array?.

But it will replace the first occurrence only. Which is the best method/approach to replace all occurrences?

回答1:

Theres no way to do that without looping.. even something like this loops internally:

string [] items = {"one","two","three","one","two","one"};

string[] items2 = items.Select(x => x.Replace("one", "zero")).ToArray();

I'm not sure why your requirement is that you can't loop.. however, it will always need to loop.

回答2:

There is one way to replace it without looping through each element:

 string [] items = {"zero","two","three","zero","two","zero"};

Other than that, you have to iterate through the array (for/lambda/foreach)

回答3:

Sorry, you have to loop. There's no getting around it.

Also, all of the other answers give you a new array with the desired elements. If you want the same array to have its elements modified, as your question implies, you should just do it like this.

for (int index = 0; index < items.Length; index++)
    if (items[index] == "one")
        items[index] = "zero";

Simple.

To avoid writing a loop in your code every time you need this to happen, create a method:

void ReplaceAll(string[] items, string oldValue, string newValue)
{
    for (int index = 0; index < items.Length; index++)
        if (items[index] == oldValue)
            items[index] = newValue;
}

Then call it like this:

ReplaceAll(items, "one", "zero");

You can also make it into an extension method:

static class ArrayExtensions
{
    public static void ReplaceAll(this string[] items, string oldValue, string newValue)
    {
        for (int index = 0; index < items.Length; index++)
            if (items[index] == oldValue)
                items[index] = newValue;
    }
}

Then you can call it like this:

items.ReplaceAll("one", "zero");

While you're at it, you might want to make it generic:

static class ArrayExtensions
{
    public static void ReplaceAll<T>(this T[] items, T oldValue, T newValue)
    {
        for (int index = 0; index < items.Length; index++)
            if (items[index].Equals(oldValue))
                items[index] = newValue;
    }
}

The call site looks the same.

Now, none of these approaches supports custom string equality checking. For example, you might want the comparison to be case sensitive, or not. Add an overload that takes an IEqualityComparer<T>, so you can supply the comparison you like; this is much more flexible, whether T is string or something else:

static class ArrayExtensions
{
    public static void ReplaceAll<T>(this T[] items, T oldValue, T newValue)
    {
        items.ReplaceAll(oldValue, newValue, EqualityComparer<T>.Default);
    }

    public static void ReplaceAll<T>(this T[] items, T oldValue, T newValue, IEqualityComparer<T> comparer)
    {
        for (int index = 0; index < items.Length; index++)
            if (comparer.Equals(items[index], oldValue))
                items[index] = newValue;
    }
}

回答4:

You can also do it in parallel:

Parallel.For(0, items.Length,
  idx => { if(items[idx] == "one") { item[idx] = "zero"; } });

回答5:

string [] items = {"one","two","three","one","two","one"};
items =  items.Select(s => s!= "one" ? s : "zero").ToArray();

Found answer from here.

回答6:

You can try this, but I think, It will do looping also.

string [] items = {"one","two","three","one","two","one"};
var str= string.Join(",", items);
var newArray = str.Replace("one","zero").Split(new char[]{','});

回答7:

string[] items = { "one", "two", "three", "one", "two", "one" };

If you want it the index way as you specified:

int n=0;
while (true)
{
n = Array.IndexOf(items, "one", n);
if (n == -1) break;
items[n] = "zero";
}

But LINQ would be better

var lst = from item in items
select item == "one" ? "zero" : item;

回答8:

string[] newarry = items.Select(str => { if (str.Equals("one")) str = "zero"; return str; }).ToArray();