我想要一种有效的方法,可以起到这样的作用
编辑:抱歉,我没有输入我之前尝试过的内容。我现在更新了这个例子。
// Method signature, Only replaces first instance or how many are specified in max
public int MyReplace(ref string source,string org, string replace, int start, int max)
{
int ret = 0;
int len = replace.Length;
int olen = org.Length;
for(int i = 0; i < max; i++)
{
// Find the next instance of the search string
int x = source.IndexOf(org, ret + olen);
if(x > ret)
ret = x;
else
break;
// Insert the replacement
source = source.Insert(x, replace);
// And remove the original
source = source.Remove(x + len, olen); // removes original string
}
return ret;
}
string source = "The cat can fly but only if he is the cat in the hat";
int i = MyReplace(ref source,"cat", "giraffe", 8, 1);
// Results in the string "The cat can fly but only if he is the giraffe in the hat"
// i contains the index of the first letter of "giraffe" in the new string
我问的唯一原因是因为我想象我的实现会因 1,000 次替换而变得缓慢。
怎么样:
public static int MyReplace(ref string source,
string org, string replace, int start, int max)
{
if (start < 0) throw new System.ArgumentOutOfRangeException("start");
if (max <= 0) return 0;
start = source.IndexOf(org, start);
if (start < 0) return 0;
StringBuilder sb = new StringBuilder(source, 0, start, source.Length);
int found = 0;
while (max-- > 0) {
int index = source.IndexOf(org, start);
if (index < 0) break;
sb.Append(source, start, index - start).Append(replace);
start = index + org.Length;
found++;
}
sb.Append(source, start, source.Length - start);
source = sb.ToString();
return found;
}
it uses StringBuilder
以避免大量中间string
s;我没有经过严格测试,但它似乎有效。它还试图避免额外的string
当没有匹配项时。
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