如何对子序列排序，并且保持原序列不变

#include<iostream>
#include<algorithm>
using namespace std;
void filter_middle(int w, int n) {
    int a[100] = { 0 }; int b[100] = { 0 }; int c[20];
    for (int i = 0; i < n; i++) {
        cin >> a[i]; b[i] = a[i];
    }
    int begin = 0;   int mid = (begin + begin + w) / 2;
    while (begin <= n - w) {//最大滤波边界 小于 滤波窗口长度
        for (int i = 0; i < w; i++) c[i] = a[begin + i];// 取出子序列，原序列保持不变
        stable_sort(c, c+w);
        b[mid+begin] = c[mid];
        begin++;
    }
    for (int i = 0; i < n; i++) {
        cout << b[i]<<" ";
    }
    cout << endl;
}
int main() {
    int w;
    int n;
    while (cin>>w>>n) {
        if (w % 2 == 0)printf("ERROR\n");
        else
            filter_middle(w, n);
    }
    return 0;
}