POJ 3659 Cell Phone Network (tree dp)

Title Link: http://poj.org/problem?id=3659

Give you a tree chart, a dot can cover the points around him, so that you cover all points with the fewest points.

Dp[i][0] means overwrite with I point, dp[i][1] means overwrite with child node, dp[i][2] means overwrite with parent node

(1) dp[i][0] = min (dp[i.son][0], dp[i.son][1], dp[i.son][2])

(2) dp[i][1] = min (dp[i.son][0], dp[i.son][1])//Special award

(3) dp[i][2] = min (dp[i.son][0], dp[i.son][1])

Note (2) that because I needs to be overwritten, dp[i.son][0] needs to take at least one.

1 //#pragma COMMENT (linker, "/stack:102400000, 102400000")2#include <algorithm>3#include <iostream>4#include <cstdlib>5#include <cstring>6#include <cstdio>7#include <vector>8#include <cmath>9#include <ctime>Ten#include <list> One#include <Set> A#include <map> - using namespacestd; -typedefLong LongLL; thetypedef pair <int,int>P; - Const intN = 1e4 +5; - intdp[n][3]; - structEdge { +     intnext, to; -}edge[n <<1]; + intHead[n], CNT; A  atInlinevoidAddintUintv) { -Edge[cnt].next =Head[u]; -Edge[cnt].to =v; -Head[u] = cnt++; - } -  in voidDfsintUintp) { -dp[u][0] =1, dp[u][1] = dp[u][2] =0; to     BOOLFlag =false; +     intMin =10000; -      for(inti = Head[u]; ~i; i =Edge[i].next) { the         intv =edge[i].to; *         if(v = =p) $             Continue;Panax Notoginseng Dfs (v, u); -dp[u][0] + = min (dp[v][0], Min (dp[v][1], dp[v][2])); thedp[u][2] + = min (dp[v][1], dp[u][0]); +         if(dp[v][0] <= dp[v][1]) { AFlag =true; thedp[u][1] + = dp[v][0]; +}Else { -dp[u][1] + = dp[v][1]; $min = min (dp[v][0]-dp[v][1], Min); $         } -     } -     if(!flag)//If you don't get dp[v][0] thedp[u][1] +=Min; - }Wuyi  the intMain () - { Wu     intN, u, v; -      while(~SCANF ("%d", &N)) { AboutMemset (Head,-1,sizeof(head)); $CNT =0; -          for(inti =1; I < n; ++i) { -scanf"%d%d", &u, &v); - Add (U, v); A Add (V, u); +         } theDfs1, -1); -printf"%d\n", Min (dp[1][0], dp[1][1])); $     } the     return 0; the}

POJ 3659 Cell Phone Network (tree dp)