洛谷P1214[USACO1.4]等差数列ArithmeticProgressions

 1 #include 
 2 using namespace std;
 3 
 4 struct node {
 5     int a, b;
 6 }w[10005];
 7 bool cmp(node a, node b) {
 8     if (a.b==b.b)
 9         return a.a<b.a;
10     return a.b<b.b;
11 }
12 
13 int n, m, a[30000], sum, ma;
14 bool b[130000], flag;
15 
16 int main() {
17     cin >> n >> m;
18     ma=m*m*2;
19     for (int i=0;i<=m;++i)
20         for (int j=0;j<=m;++j)
21             if (!b[i*i+j*j])
22                 b[i*i+j*j]=true, a[++a[0]]=i*i+j*j;
23     sort(a+1, a+a[0]+1);
24     for (int i=1;i<=a[0]-n+1;++i)
25         for (int j=i+1;j<=a[0]-n+2;++j) {
26             int c=a[j]-a[i], t=n-2, no=a[j];
27             flag=true;
28             if (no+c*t>ma)
29                 break;
30             while (t--) {
31                 no+=c;
32                 if (!b[no]) {
33                     flag=false;
34                     break;
35                 }
36             }
37             if (flag) {
38                 sum++;
39                 w[sum].a=a[i], w[sum].b=c;
40             }
41         }
42     sort(w+1, w+sum+1, cmp);
43     if (sum==0)
44         cout <<"NONE\n";
45     for (int i=1;i<=sum;++i)
46         printf("%d %d\n", w[i].a, w[i].b);
47 }