UVA 11853 paintball--(dfs+ round)

　　Test instructions: Give a 1000*1000 size matrix, there are a number of circles, indicating obstacles, now to find a path from the left to the right, the output entrance and exit coordinates, if there are many answers, output y value the largest answer.

Analysis: Starting with the circle connected to the DFS, each to find the intersection with the DFS path, if you can access to the following, then the left and right is definitely not connected; and update the maximum Y-value answer at DFS.

See the code for details:

1#include <stdio.h>2#include <algorithm>3#include <string.h>4#include <Set>5#include <math.h>6 using namespacestd;7 Const intN = ++5;8 Const intINF =2e9;9typedefLong Longll;Tentypedef pair<int,int>PII; One  A intN; - intVis[n]; - structCircle the { -     intX,y,r; -     voidRead () -     { +scanf"%d%d%d",&x,&y,&R); -     } + }c[n]; A  at BOOLCan (Circle A,circle b) - { -     DoubleDX = a.x-b.x; -     DoubleDY = a.y-b.y; -     DoubleD = sqrt (dx*dx+dy*dy); -     returnD <= A.R +B.R; in } -  to DoubleAnsl =0, AnsR =0; + voidUpdateintu) - { the     if(c[u].x <=C[U].R) *     { $         Doublet = sqrt (c[u].r*c[u].r-c[u].x*c[u].x);Panax Notoginseng         Doublepos = c[u].y-T; -Ansl =min (Ansl, POS); the     } +     if(c[u].x + C[U].R >= +) A     { the         Doublett =1000.0-c[u].x; +         Doublet = sqrt (c[u].r*c[u].r-tt*TT); -         Doublepos = c[u].y-T; $AnsR =min (AnsR, POS); $     } - } -  the BOOLDfsintu) - {WuyiVis[u] =1; the     if(C[u].y <= C[U].R)return false; - update (u); Wu      for(intI=1; i<=n;i++) -     { About         if(!vis[i] &&can (C[u], c[i])) $         { -             if(!dfs (i))return false; -         } -     } A     return true; + } the  - voidSolve () $ { theAnsl = +, AnsR = +; thememset (Vis,0,sizeof(Vis)); the      for(intI=1; i<=n;i++) the     { -         if(!vis[i] && c[i].y + C[I].R >= +) in         { the             if(!DFS (i)) the             { AboutPuts"Impossible"); the                 return ; the             } the         } +     } -printf"0.00%.2f 1000.00%.2f\n", ANSL,ANSR); the }Bayi  the intMain () the { -      while(SCANF ("%d", &n) = =1) -     { the          for(intI=1; i<=n;i++) C[i].read (); the solve (); the     } the     return 0; -}

UVA 11853 paintball--(dfs+ round)