这个代码是我复制别人的，有一个不懂的地方，请指教

就是为什么while循环里的s不另开一个变量临时存s，r让k<=s;而让s-=k;这样s不是越减越小了吗？循环次数不会变少吗

#include <iostream>
#include <algorithm>

using namespace std;

const int N = 12010, M = 2010;

int n, m;
int v[N], w[N];
int f[M];

int main()
{
    cin >> n >> m;

    int cnt = 0;
    for (int i = 1; i <= n; i ++ )
    {
        int a, b, s;
        cin >> a >> b >> s;
        int k = 1;
        while (k <= s)
        {
            cnt ++ ;
            v[cnt] = a * k;
            w[cnt] = b * k;
            s -= k;
            k *= 2;
        }
        if (s > 0)
        {
            cnt ++ ;
            v[cnt] = a * s;
            w[cnt] = b * s;
        }
    }

    n = cnt;

    for (int i = 1; i <= n; i ++ )
        for (int j = m; j >= v[i]; j -- )
            f[j] = max(f[j], f[j - v[i]] + w[i]);

    cout << f[m] << endl;

    return 0;
}

yxc