ACM 组合数学

//C(n,r)int c(int n,int r){    int c=1;    for(int i=0;i<r;i++) c=c*(n-i)/(i+1);    return c;}//排列生成函数 next_permutation    string str;    cin >> str;    sort(str.begin(), str.end());    cout << str << endl;    while(next_permutation(str.begin(), str.end())){        cout << str << endl;    }//母函数模板const int maxn = 10010;int c1[maxn], c2[maxn];int main(){    int num;    int i,j,k;      while(~scanf("%d", &num)){        for(int i = 0; i <= num; i++){            c1[i] = 1;            c2[i] = 0;        }        for(int i = 2; i <= num; i++){            for(int j = 0; j <= num; j++){                for(int k = 0; k+j <= num; k += i){                    c2[j+k] += c1[j];                }            }            for(int j = 0; j <= num; j++){                c1[j] = c2[j];                c2[j] = 0;            }        }    printf("%d\n", c1[num]);    }}