{"id":327,"date":"2013-02-07T16:00:00","date_gmt":"2013-02-07T08:00:00","guid":{"rendered":"http:\/\/nike0good.jp1.rpvhost.net\/232"},"modified":"2013-02-07T16:00:00","modified_gmt":"2013-02-07T08:00:00","slug":"poj_1741_men_q8-tree-point_divide-and-conquer","status":"publish","type":"post","link":"https:\/\/nike0good.com\/?p=327","title":{"rendered":"POJ 1741(\u7537\u4eba\u516b\u9898-Tree-\u70b9\u5206\u6cbb)"},"content":{"rendered":"\n\n\n
\n
Language:\n\n\n\n
Time Limit:<\/strong> 1000MS<\/td>\n <\/td>\nMemory Limit:<\/strong> 30000K<\/td>\n<\/tr>\n
Total Submissions:<\/strong> 6982<\/td>\n <\/td>\nAccepted:<\/strong> 2010<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n

Description<\/p>\n

\n\u7ed9\u5b9a\u4e00\u68f5 N (1\u2264<\/span> N\u2264<\/span> 10000) \u4e2a\u7ed3\u70b9\u7684\u5e26\u6743(\u22641000<\/span>)\u6811\uff0c\u5b9a\u4e49
\n dist(u, v) \u4e3a u, v \u4e24\u70b9\u95f4\u7684\u6700\u77ed\u8def\u5f84\u957f\u5ea6\uff0c \u8def\u5f84\u7684\u957f\u5ea6\u5b9a\u4e49\u4e3a\u8def\u5f84\u4e0a\u6240\u6709\u8fb9\u7684\u6743\u548c\u3002\u518d\u7ed9\u5b9a\u4e00\u4e2a K (1\u2264<\/span> K\u2264<\/span> 10 ) \uff0c\u5982\u679c\u5bf9\u4e8e\u4e0d\u540c\u7684\u4e24\u4e2a\u7ed3\u70b9 a, b \uff0c\u5982\u679c\u6ee1 \u8db3 dist
\n (a, b)\u2264<\/span> K \uff0c\u5219\u79f0 (a, b) \u4e3a\u5408\u6cd5\u70b9\u5bf9\u3002 \u6c42\u5408\u6cd5\u70b9\u5bf9\u4e2a\u6570\u3002\n<\/div>\n

Input<\/p>\n

\n\u6709\u5f88\u591a\u6570\u636e. \u6bcf\u7ec4\u6570\u636e\u7b2c\u4e00\u884c\u4e3a n, k. (n<=10000) \u63a5\u4e0b\u6765 n-1 \u884c\u4e3a u,v,w, \u8868\u793au\u548cv\u4e4b\u95f4\u6709\u4e00\u6761\u6743\u4e3aw\u7684\u8fb9. 
\n\u6570\u636e\u4ee5\u20180 0\u2019\u7ed3\u5c3e. \n<\/div>\n

Output<\/p>\n

\n\u5bf9\u6bcf\u7ec4\u6570\u636e\u8f93\u51fa\u4e00\u884c\u5408\u6cd5\u70b9\u5bf9\u4e2a\u6570.<\/div>\n

Sample Input<\/p>\n

5 4\n1 2 3\n1 3 1\n1 4 2\n3 5 1\n0 0\n<\/pre>\n
Sample Output<\/p>\n
8<\/pre>\n
Source<\/p>\n
\nLouTiancheng@POJ<\/a><\/div>\n<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
\u5728\u6f06\u5b50\u8d85\u7684\u8bba\u6587<\/a>\u91cc\u6709\u8be5\u9898\u7684\u8be6\u7ec6\u89e3\u9898\u62a5\u544a<\/span>\u3002<\/span><\/p>\n
\u5728\u8fd9\u91cc\u7b80\u5355\u8bf4\u8bf4\u6811\u94fe\u5256\u5206\u4e2dcenter_node\u7684\u9009\u53d6\u3002<\/span><\/p>\n
center_node\u4e3a\u4e00\u68f5\u5b50\u6811\u4e2d\u7684\u4e00\u4e2a\u80fd\u4f7f\u5176\u4e3a\u6839\u8282\u70b9\u65f6\uff0c\u5176\u7684\u5b50\u6811\u7684\u6700\u5927\u7ed3\u70b9\u6570\u6700\u5c0f\u7684\u7684\u7ed3\u70b9\u3002<\/span><\/p>\n
\u4e5f\u5c31\u662f\u4f7f\u5b50\u6811\u7684max_siz\u6700\u5c0f<\/span><\/p>\n
\u56e0\u4e3a\u6362\u4e86root\uff0c\u5fc5\u987b\u7528b\u8bb0\u5f55\uff0c\u9632\u6b62\u8d70\u5230\u5b50\u6811\u5916\u53bb\u3002<\/span><\/p>\n

\n<\/span><\/p>\n
\u91cd\u513f\u5b50\uff1a\u4e00\u4e2a\u8282\u70b9\u7684\u513f\u5b50\u4e2dsiz\u6700\u5927\u7684\u90a3\u4e2a(hson)<\/span><\/p>\n

\n<\/span><\/p>\n
<\/span><\/p>\n
#include<cstring>\n#include<cstdlib>\n#include<cstdio>\n#include<cmath>\n#include<iostream>\n#include<functional>\n#include<algorithm>\nusing namespace std;\n#define MAXN (10000+10)\nint n,k;\nint edge[MAXN*2],pre[MAXN],next[MAXN*2],weight[MAXN*2],size=0;\nbool b[MAXN];\nvoid addedge(int u,int v,int w)\n{\n\tedge[++size]=v;\n\tweight[size]=w;\n\tnext[size]=pre[u];\n\tpre[u]=size;\n}\nint dis[MAXN],deep[MAXN],siz[MAXN],max_sub_siz[MAXN],tot;\nint que[MAXN],q_n;\nvoid get_center_dfs(int u,int fa)\n{\n\tsiz[u]=1;que[++q_n]=u;max_sub_siz[u]=0;\n\tfor (int p=pre[u];p;p=next[p])\n\t{\n\t\tint &v=edge[p];\n\t\tif (v!=fa&&!b[v])\n\t\t{\n\t\t\tget_center_dfs(v,u);siz[u]+=siz[v];\n\t\t\tmax_sub_siz[u]=max(max_sub_siz[u],siz[v]);\n\t\t}\n\t}\n\n}\nint get_center(int u,int fa)\n{\n\tint minhson=n,mini=0;q_n=0;\n\tget_center_dfs(u,fa);\n\tfor (int i=1;i<=q_n;i++)\n\t{\n\t\tmax_sub_siz[que[i]]=max(max_sub_siz[que[i]],q_n-siz[que[i]]);\n\t\tif (minhson>max_sub_siz[que[i]])\n\t\t{\n\t\t\tminhson=max_sub_siz[que[i]];\n\t\t\tmini=que[i];\n\t\t}\n\t}\n\treturn mini;\n}\nvoid getdis(int u,int d,int fa)\n{\n\tdis[++tot]=d;\n\tfor (int p=pre[u];p;p=next[p])\n\t{\n\t\tint &v=edge[p];\n\t\tif (v!=fa&&!b[v])\n\t\t{\n\t\t\tgetdis(v,d+weight[p],u);\n\t\t}\n\t}\n}\nint count_dis(int l,int r)\n{\n\tint i=l,j=r,ans=0;sort(dis+l,dis+r+1);\n\twhile (i<j)\n\t{\n\t\tif (dis[i]+dis[j]<=k) ans+=j-(i++);\n\t\telse j--;\n\t}\n\treturn ans;\n}\nint dfs_main(int u,int fa)\n{\n\tint root=get_center(u,fa),ans=0;\n\ttot=0;\n\tb[root]=1;\n\tfor (int p=pre[root];p;p=next[p]) \/\/root\n\t{\n\t\tint &v=edge[p];\n\t\tif (v!=fa&&!b[v])\n\t\t{\n\t\t\tint l=tot+1;\n\t\t\tgetdis(v,weight[p],root);\n\t\t\tans-=count_dis(l,tot);\n\t\t}\n\t}\n\tdis[++tot]=0;\n\tans+=count_dis(1,tot);\n\tfor (int p=pre[root];p;p=next[p])\n\t{\n\t\tint &v=edge[p];\n\t\tif (v!=fa&&!b[v])\n\t\t{\n\t\t\tans+=dfs_main(v,root);\n\t\t}\n\t}\n\treturn ans;\n}\nint main()\n{\n\/\/\tfreopen("poj1741.in","r",stdin);\n\twhile (scanf("%d%d",&n,&k)&&(n+k))\n\t{\n\t\tmemset(pre,0,sizeof(pre));size=0;\n\t\tmemset(b,0,sizeof(b));\n\t\tint u,v,w;\n\t\tfor (int i=1;i<n;i++)\n\t\t{\n\t\t\tscanf("%d%d%d",&u,&v,&w);\n\t\t\taddedge(u,v,w);addedge(v,u,w);\n\t\t}\n\t\tcout<<dfs_main(edge[1],0)<<endl;\n\t}\n\treturn 0;\n}<\/pre>\n
<\/p>\n","protected":false},"excerpt":{"rendered":"
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