我的代码（一直显示错,dev可以运行）：

#include<bits/stdc++.h>
using namespace std;
const int MAX=1e4;
int index,a[MAX],ans=0;
void step(int n,int k){
	if(n==0){
		ans++;
		return;
	}
	index++; 
	a[index]=1;
	step(n-1,k);
	index--;
	for(int i=1;i<k;i++){
		if(n>i){
			index++;
			a[index]=i+1;
			step(n-i-1,k);
			index--;
		}
	}
	return;
}
int n,k;
int main(){
	cin>>n>>k;
	step(n,k);
	cout<<ans<<'\n';
	return 0;
}

报错信息是：

/tmp/compiler_u7zkxw6v/src:4:5: 错误：‘int index’ redeclared as different kind of entity
    4 | int index,a[MAX],ans=0;
      |     ^~~~~
In file included from /nix/store/79624djlfdc0a6anji2rwqd9p9ycqi8h-glibc-2.34-210-dev/include/string.h:446,
                 from /nix/store/bbmwawbq7wjb54fa35wr72alcm083d1f-luogu-gcc-9.3.0/include/c++/9.3.0/cstring:42,
                 from /nix/store/bbmwawbq7wjb54fa35wr72alcm083d1f-luogu-gcc-9.3.0/include/c++/9.3.0/x86_64-unknown-linux-gnu/bits/stdc++.h:48,
                 from /tmp/compiler_u7zkxw6v/src:1:
/nix/store/79624djlfdc0a6anji2rwqd9p9ycqi8h-glibc-2.34-210-dev/include/strings.h:61:1: 附注：previous declaration ‘const char* index(const char*, int)’
   61 | index (const char *__s, int __c) __THROW
      | ^~~~~
/tmp/compiler_u7zkxw6v/src: 在函数‘int step(int, int)’中:
/tmp/compiler_u7zkxw6v/src:10:7: 错误：类型没有后自增运算符
   10 |  index++;
      |       ^~
/tmp/compiler_u7zkxw6v/src:11:9: 错误：‘int [10000][<未解决的重载函数类型>]’用作数组下标类型无效
   11 |  a[index]=1;
      |         ^
/tmp/compiler_u7zkxw6v/src:13:7: 错误：类型没有后自减运算符
   13 |  index--;
      |       ^~
/tmp/compiler_u7zkxw6v/src:16:9: 错误：类型没有后自增运算符
   16 |    index++;
      |         ^~
/tmp/compiler_u7zkxw6v/src:17:11: 错误：‘int [10000][<未解决的重载函数类型>]’用作数组下标类型无效
   17 |    a[index]=i+1;
      |           ^
/tmp/compiler_u7zkxw6v/src:19:9: 错误：类型没有后自减运算符
   19 |    index--;
      |         ^~