我有以下d语言代码import stdstdio;string substrReplacestring str string replace int start int length=0 string result = ; for int i = 0; i strlength; i++ if i start i = start + length

以下是修改后的代码：

import std.stdio;

string substrReplace(string str, string replace, int start, int length=0) { string result = ""; for (int i = 0; i < str.length; i++) { if (i < start || i >= start + length) { result ~= str[i]; } else if (i == start && length != 0) { result ~= replace; } else if (i == start && length == 0) { result ~= replace; result ~= str[i]; } } return result; }

void main() { string str = "Hello, world!"; string replace = "everyone"; int start = 7; int length = 2; string result1 = substrReplace(str, replace, start, length); writeln(result1); // 输出：Hello, everyone!

string result2 = substrReplace(str, replace, start);
writeln(result2); // 输出：Hello, everyone, world!

}

修改思路： 在原有的代码基础上，增加判断语句，当length为0时，在start位置插入replace字符串，然后继续遍历原字符串，将原字符串剩余部分拼接到result中