Two methods of Codeforces 510B non-circular graph finding (search and set)

Topic Connection: Http://codeforces.com/problemset/problem/510/B

Solution:

1. Dfs
   Each time the value of the parent node is recorded and passed down, judge the new reach node:
   (1) did not walk → continue to search;
   (2) Walk && Not parent node (for the number of steps also to >=4) → Find the ring;

2. and check Set
   Each node is mapped into a i*m+j from the starting point, respectively, and then add it to the right side of the node, if it is found that a node is already in the collection, then the ring has been found.

   • Dfs:

#include <cstdio>#include <cstdlib>#include <cstring>#include <cmath>//////////////////////#include <iostream>#include <algorithm>#include <string>#include <iterator>#include <sstream>#include <functional>#include <numeric>///////////////////////#include <vector>#include <map>#include <stack>#include <queue>#include <set>#include <bitset>#include <list>using namespace STD;#define LCH (x) ((x) << 1)#define RCH (x) ((x) <<1|1)#define DAD (x) ((x) >>1)#define LOWBIT (x) ((x) & ( -X))typedef  Long Long intLL;Const intINF =0x4f4f4f4f;Const DoubleEPS =1e-6;Const Long DoublePI =ACOs(0.0) *2.0;Const intN = -+Ten;intN,m;CharMaze[n][n];BOOLVis[n][n];Const intDx[] = {0,1,0,-1};Const intDy[] = {1,0,-1,0};BOOLOkBOOLDfsintXintYintPxintPyintCNT);intMain () {//freopen ("In.txt", "R", stdin);     while(scanf("%d%d%*c", &n,&m) = =2)    {memset(Vis,0,sizeof(VIS)); for(inti =0; I < n;        i++) gets (Maze[i]); OK =0; for(inti =0; I < n; i++) for(intj =0; J < M; J + +)if(!vis[i][j])if(Dfs (i,j,-1,-1,1))                      {puts("Yes");return 0; }puts("No"); }return 0;}BOOLDfsintXintYintPxintPyintCNT) {Vis[x][y] =1; for(inti =0; I <4; i++) {intNX = x +dx[i], NY = y + dy[i];if(0<= NX && NX < n &&0<= NY && NY < m && Maze[nx][ny] = Maze[x][y]) {if(!vis[nx][ny]) DFS (nx,ny,x,y,cnt+1);Else if((NX! = PX | | NY! = PY) && cnt>=4) OK =1; }    }returnOK;}

• And check the set:

#include <cstdio>#include <cstdlib>#include <cstring>#include <cmath>//////////////////////#include <iostream>#include <algorithm>#include <string>#include <iterator>#include <sstream>#include <functional>#include <numeric>///////////////////////#include <vector>#include <map>#include <stack>#include <queue>#include <set>#include <bitset>#include <list>using namespace STD;#define LCH (x) ((x) << 1)#define RCH (x) ((x) <<1|1)#define DAD (x) ((x) >>1)#define LOWBIT (x) ((x) & ( -X))typedef  Long Long intLL;Const intINF =0x4f4f4f4f;Const DoubleEPS =1e-6;Const Long DoublePI =ACOs(0.0) *2.0;Const intN =10000+Ten;intPre[n];int_rank[n];CharMaze[n][n];intFindintx);intJoinintXinty);voidInivoid);intSame (intXinty);intMain () {ini ();intN,m;scanf("%d%d%*c", &n,&m); for(inti =0; I < n; i++) gets (Maze[i]); for(inti =0; I < n; i++) { for(intj =0; J < M; J + +) {if(Maze[i][j] = = maze[i+1][J] && i <n-1)            {if(Same (I*m+j, (i+1) (*m+j)) {puts("Yes");return 0; }ElseJoin (I*m+j, (i+1) *m+j); }if(Maze[i][j] = = maze[i][j+1] && J < m1)            {if(Same (i*m+j,i*m+j+1))   {puts("Yes");return 0; }ElseJoin (i*m+j,i*m+j+1); }        }    }puts("No");return 0;}voidInivoid){intI for(i =0; i < N; i++) Pre[i] = i,_rank[i]=0;}intJoinintXintY) {intFX = Find (x), FY = find (y);if(FX = = FY)return 0;if(_rank[fx] > _rank[fy])    {Pre[fy] = FX; }Else{PRE[FX] = FY;if(_rank[fx] = = _rank[fy]) _rank[fy]++; }}//simplified notation, using recursion//int find (int x) {return x==pre[x]?x:pre[x]=find (pre[x]);}intFind (intx) {intR = x; while(r! = Pre[r]) R = Pre[r];inti = x,j; while(r! = Pre[i])        {j = pre[i];        Pre[i] = r;    i = j; }returnR;}intSame (intXintY) {returnFind (x) = = Find (y);}

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Two methods of Codeforces 510B non-circular graph finding (search and set)