学了一早上倍增，感觉lca还是tarjan好写。
poj1330
1 #include <stdio.h>
2 #include <string.h>
3 #include <queue>
4 #include <algorithm>
5 #define DEG 20//2^20
6 #define maxn 10010
7 using namespace std;
8 struct node
9 {
10 int v, next;
11 }a[maxn*2];
12 int q[4*maxn], fa[maxn][DEG], root, n, m, u, v, tot, first[maxn*2], dis[maxn];
13 bool flag[maxn];
14 void addedge(int st, int end)
15 {
16 a[tot].v = end;
17 a[tot].next = first[st]; first[st] = tot++;
18 }
19 void init()
20 {
21 tot = 0;
22 memset(first, -1, sizeof(first));
23 memset(flag, 0, sizeof(flag));
24 }
25 void bfs(int root)
26 {
27 queue<int >que;
28 dis[root] = 0;
29 fa[root][0] = root;//root‘s 2^0 father is root
30 que.push(root);
31 //q[0] = root;
32 //int head = 0,tail = 1;
33 while (!que.empty())
34 {
35 //int u = q[head++];
36 int u = que.front();que.pop();
37 for (int i = 1; i < DEG; i++)/*the father from 2^1 ~ 2^DEG*/fa[u][i] = fa[fa[u][i-1]][i-1];//u‘s 2^i father is u‘s (2^(i-1))^(i-1)
38 for (int e = first[u]; e != -1; e = a[e].next)
39 {
40 int v = a[e].v;
41 if (v == fa[u][0])continue;//if u‘s father is v,continue, it can‘t vis his fahter
42 dis[v] = dis[u] + 1;
43 fa[v][0] = u;
44 //q[++tail] = v;
45 que.push(v);
46 }
47 }
48 }
49 int LCA(int u, int v)
50 {
51 if (dis[u] > dis[v])swap(u, v);
52 int du = dis[u], dv = dis[v];
53 int tu = u, tv = v;
54 for (int det = dv - du, i = 0;det; det>>=1, i++)
55 if (det&1)//det if u‘s high - v‘s high;
56 tv = fa[tv][i];//let deeper point up(2^i) until det = 1;
57 if (tu == tv)return tu;
58 for (int i = DEG - 1; i >= 0; i--)
59 {
60 if (fa[tu][i] == fa[tv][i])continue;
61 tu = fa[tu][i];
62 tv = fa[tv][i];
63 }
64 return fa[tu][0];
65 }
66 int main()
67 {
68 int T;
69 scanf("%d", &T);
70 while (T--)
71 {
72 scanf("%d", &n);
73 init();
74 for (int i = 1; i < n; i++)
75 {
76 scanf("%d %d", &u, &v);
77 addedge(u, v);addedge(v, u);
78 flag[v] = 1;
79 }
80 int root;
81 for (int i = 1; i <= n; i++)
82 {
83 if (!flag[i])
84 {
85 root = i;break;
86 }
87 }
88 bfs(root);//dfs(root);
89 scanf("%d %d", &u, &v);
90 printf("%d\n", LCA(u,v));
91 }
92 }
bzoj3732
1 /**************************************************************
2 Problem: 3732
3 User: z52527
4 Language: C++
5 Result: Accepted
6 Time:392 ms
7 Memory:7304 kb
8 ****************************************************************/
9
10 #include <stdio.h>
11 #include <string.h>
12 #include <algorithm>
13 #define DEG 20//2^20
14 #define maxn 30010
15 using namespace std;
16 struct node
17 {
18 int u, v, w, next;
19 }a[maxn], b[maxn];
20 int first[maxn], m, n, q, tot;
21 int dis[maxn], fa[maxn][DEG], maxf[maxn][DEG], ans, father[maxn];
22 void addedge(int st, int end, int val)
23 {
24 b[++tot].u = st;b[tot].v = end;b[tot].w = val;
25 b[tot].next = first[st]; first[st] = tot;
26 }
27 int getfather(int x){return father[x] == x ? x : getfather(father[x]);}
28 int cmp (node a, node b){return a.w < b.w;}
29 int dfs(int u)
30 {
31 dis[u] = dis[fa[u][0]]+1;
32 for (int e = first[u]; e != -1; e = b[e].next)
33 {
34 if (b[e].v == fa[u][0]) continue;
35 fa[b[e].v][0] = u;
36 maxf[b[e].v][0] = b[e].w;
37 dfs(b[e].v);
38 }
39 }
40 int lca(int u, int v)
41 {
42 ans = 0;
43 if (dis[u] > dis[v])swap(u, v);
44 int du = dis[u], dv = dis[v];
45 int fu = u, fv = v;
46 for (int def = dv - du, i = 0; def; def>>=1, i++)
47 if (def&1)
48 ans = max(ans, maxf[fv][i]), fv = fa[fv][i];
49 if (fu == fv)return ans;
50 for (int i = 14; i >=0; i--)
51 {
52 if (fa[fu][i] == fa[fv][i])continue;
53 ans = max(maxf[fu][i], ans);
54 ans = max(maxf[fv][i], ans);
55 fu = fa[fu][i];
56 fv = fa[fv][i];
57 }
58 ans = max(maxf[fu][0], ans);
59 ans = max(maxf[fv][0], ans);
60 return ans;
61 }
62 int main()
63 {
64 int u, v, w;
65 scanf("%d %d %d", &n, &m, &q);
66 for (int i = 1; i <= n; i++)father[i] = i;
67 memset(first, -1, sizeof(first));
68 for (int i = 1; i <= m; i++)
69 {
70 scanf("%d %d %d", &u, &v, &w);
71 a[i].u = u;a[i].v = v;a[i].w = w;
72 }
73 sort(a+1, a+1+m, cmp);
74 for (int i = 1; i <= m; i++)
75 {
76 u = getfather(a[i].u);
77 v = getfather(a[i].v);
78 if (u != v)
79 {
80 father[u] = v;
81 addedge(a[i].u, a[i].v, a[i].w);
82 addedge(a[i].v, a[i].u, a[i].w);
83 }
84 }
85 dfs(1);
86 //scanf("%d", &q);
87 for(int j = 1;j <= 14; j++)
88 for(int i = 1;i <= n; i++)
89 fa[i][j] = fa[ fa[i][j-1] ][j-1],maxf[i][j]=max( maxf[i][j-1] , maxf[ fa[i][j-1] ][j-1] );
90 for (int i = 1; i <= q; i++)
91 {
92 scanf("%d %d", &u, &v);
93 printf("%d\n", lca(u, v));
94 }
95 }
noip2013 货车运输
1 #include <stdio.h>
2 #include <string.h>
3 #include <algorithm>
4 #define DEG 20//2^20
5 #define maxn 50010
6 using namespace std;
7 struct node
8 {
9 int u, v, w, next;
10 }a[maxn], b[maxn];
11 int first[maxn], m, n, q, tot;
12 int dis[maxn], fa[maxn][DEG], maxf[maxn][DEG], ans, father[maxn];
13 void addedge(int st, int end, int val)
14 {
15 b[++tot].u = st;b[tot].v = end;b[tot].w = val;
16 b[tot].next = first[st]; first[st] = tot;
17 }
18 int getfather(int x){return father[x] == x ? x : getfather(father[x]);}
19 int cmp (node a, node b){return a.w > b.w;}
20 int dfs(int u)
21 {
22 dis[u] = dis[fa[u][0]]+1;
23 for (int e = first[u]; e != -1; e = b[e].next)
24 {
25 if (b[e].v == fa[u][0]) continue;
26 fa[b[e].v][0] = u;
27 maxf[b[e].v][0] = b[e].w;
28 dfs(b[e].v);
29 }
30 }
31 int lca(int u, int v)
32 {
33 ans = 2000000000;
34 if (dis[u] > dis[v])swap(u, v);
35 int du = dis[u], dv = dis[v];
36 int fu = u, fv = v;
37 for (int def = dv - du, i = 0; def; def>>=1, i++)
38 if (def&1)
39 ans = min(ans, maxf[fv][i]), fv = fa[fv][i];
40 if (fu == fv)return ans;
41 for (int i = 16; i >= 0; i--)
42 {
43 if (fa[fu][i] == fa[fv][i])continue;
44 ans = min(maxf[fu][i], ans);
45 ans = min(maxf[fv][i], ans);
46 fu = fa[fu][i];
47 fv = fa[fv][i];
48 }
49 ans = min(maxf[fu][0], ans);
50 ans = min(maxf[fv][0], ans);
51 return ans;
52 }
53 int main()
54 {
55 int u, v, w;
56 scanf("%d %d", &n, &m);
57 for (int i = 1; i <= n; i++)father[i] = i;
58 memset(first, -1, sizeof(first));
59 for (int i = 1; i <= m; i++)
60 {
61 scanf("%d %d %d", &u, &v, &w);
62 a[i].u = u;a[i].v = v;a[i].w = w;
63 }
64 sort(a+1, a+1+m, cmp);
65 for (int i = 1; i <= m; i++)
66 {
67 u = getfather(a[i].u);
68 v = getfather(a[i].v);
69 if (u != v)
70 {
71 father[u] = v;
72 addedge(a[i].u, a[i].v, a[i].w);
73 addedge(a[i].v, a[i].u, a[i].w);
74 }
75 }
76 dfs(1);
77 scanf("%d", &q);
78 for(int j = 1;j <= 16; j++)
79 for(int i = 1;i <= n; i++)
80 fa[i][j] = fa[ fa[i][j-1] ][j-1],maxf[i][j]=min( maxf[i][j-1] , maxf[ fa[i][j-1] ][j-1] );
81 for (int i = 1; i <= q; i++)
82 {
83 scanf("%d %d", &u, &v);
84 if (getfather(u) != getfather(v)){printf("-1\n");continue;}
85 printf("%d\n", lca(u, v));
86 }
87 }
时间： 2024-10-12 14:38:49