海口企业网站建设制作哪家专业,建一个电商平台多少钱,消息网站怎么做,我做的网站打开慢怎么处理P2634 [国家集训队]聪聪可可#xff08;树上启发式合并#xff09;
题意#xff1a;
一颗n个点的树#xff0c;问其中两点之间的边上数的和加起来是3的倍数的点对有多少个#xff1f; 输出这样的点对所占比例
题解#xff1a;
没有修改#xff0c;统计边长为3的倍数…P2634 [国家集训队]聪聪可可树上启发式合并
题意
一颗n个点的树问其中两点之间的边上数的和加起来是3的倍数的点对有多少个 输出这样的点对所占比例
题解
没有修改统计边长为3的倍数经典的树上路径统计树上启发式请求一战 但是调了一阵子没调出来我对dsu的理解还是不够深
代码
待修改代码
#include bits/stdc.h
#include unordered_map
#define debug(a, b) printf(%s %d\n, a, b);
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pairint, int PII;
clock_t startTime, endTime;
//Fe~Jozky
const ll INF_ll 1e18;
const int INF_int 0x3f3f3f3f;
void read(){};
template typename _Tp, typename... _Tps void read(_Tp x, _Tps... Ar)
{x 0;char c getchar();bool flag 0;while (c 0 || c 9)flag| (c -), c getchar();while (c 0 c 9)x (x 3) (x 1) (c ^ 48), c getchar();if (flag)x -x;read(Ar...);
}
template typename T inline void write(T x)
{if (x 0) {x ~(x - 1);putchar(-);}if (x 9)write(x / 10);putchar(x % 10 0);
}
void rd_test()
{
#ifdef LOCALstartTime clock();freopen(in.txt, r, stdin);
#endif
}
void Time_test()
{
#ifdef LOCALendTime clock();printf(\nRun Time:%lfs\n, (double)(endTime - startTime) / CLOCKS_PER_SEC);
#endif
}
const int maxn 1e5 9;
vectorPII vec[maxn];
int sz[maxn];
int dis[maxn];
int son[maxn];
int Son;
int num[3];
int ans 0;
void dfs_son(int u, int fa)
{sz[u] 1;for (auto it : vec[u]) {int v it.first;int w it.second;if (v fa)continue;dis[u] dis[fa] w;dfs_son(v, u);sz[u] sz[v];if (sz[v] sz[son[u]])son[u] v;}
}
void cal(int u, int fa, int LCA)
{int x ((dis[LCA] - dis[u]) % 3 3) % 3;ans num[x];for (auto it : vec[u]) {int v it.first;if (v ! fa v ! son[u])cal(v, u, LCA);}
}
void add(int u, int fa, int val, int LCA)
{int Dis (dis[u] - dis[LCA]) % 3;num[Dis] val;for (auto it : vec[u]) {int v it.first;if (v ! fa v ! son[u])add(v, u, val, LCA);}
}
void work(int u, int fa, int keep)
{for (auto it : vec[u]) {int v it.first;if (v ! fa v ! son[u])work(v, u, 0);}if (son[u]) {work(son[u], u, 1);Son son[u];}add(u, fa, 1, u);Son 0;cal(u, fa, u);if (!keep) {add(u, fa, -1, u);}
}
int main()
{//rd_test();int n;read(n);for (int i 1; i n; i) {int u, v, w;read(u, v, w);vec[u].push_back({v, w});vec[v].push_back({u, w});}dis[1] 1;dfs_son(1, 0);work(1, 0, 1);ll a ans n;ll b 1ll * n * n;ll g __gcd(a, b);printf(%lld/%lld\n, a / g, b / g);//Time_test();
}
洛谷上的AC代码
#include bits/stdc.h
using namespace std;
#define For(pos) for (int k First[pos]; k; k Next[k])
const int Maxn 2e4 5;
int n, First[Maxn], to[Maxn * 2], Next[Maxn * 2], W[Maxn * 2], cnt;
int son[Maxn], size[Maxn], deep[Maxn];
inline void add(int z, int y, int w)
{Next[cnt] First[z];First[z] cnt;to[cnt] y;W[cnt] w;
}
int ans 0, P;
inline int R()
{char c;int sign 1, res 0;while ((c getchar()) 9 || c 0)if (c -)sign -1;res c - 0;while ((c getchar()) 0 c 9)res res * 10 c - 0;return res * sign;
}
void deal(int pos, int father)
{size[pos] 1;For(pos){if (to[k] father)continue;deep[to[k]] deep[pos] W[k];deal(to[k], pos);size[pos] size[to[k]];if (size[son[pos]] size[to[k]])son[pos] to[k];}
}
int q[4];inline void cal(int pos, int LCA)
{int x (2 * deep[LCA] - deep[pos]) % 3 3;x x % 3;ans q[x];
}
void work(int pos, int father, bool ca, int LCA)
{if (ca)cal(pos, LCA);elseq[deep[pos] % 3];For(pos){if (to[k] father)continue;work(to[k], pos, ca, LCA);}
}
void dfs(int pos, int father, bool heavy)
{For(pos) if (to[k] ! father to[k] ! son[pos]){dfs(to[k], pos, 0);}if (son[pos])dfs(son[pos], pos, 1);For(pos){if (to[k] father || to[k] son[pos])continue;work(to[k], pos, 1, pos);work(to[k], pos, 0, pos);}cal(pos, pos);q[deep[pos] % 3];if (!heavy)q[0] q[1] q[2] 0;
}
int main()
{n R();int a, b, w;for (int i 1; i n; i) {a R();b R();w R();add(a, b, w);add(b, a, w);}deal(1, 0);dfs(1, 0, 1);ans ans * 2 n;int di n * n;for (int i 2; i ans; i)while (ans % i 0 di % i 0) {ans/ i;di/ i;}if (ans di)puts(1/1);elseprintf(%d/%d\n, ans, di);
}
