Problem:A head to tail ordering of strings is the one in which the last letter of the previous word is the same as the first letter of the following word. For eg. ‘Angular’can be followed by ‘ rotation’.
The task is to write a code to accept a set of finite strings and determine if such an ordering is possible by arranging them in a head to tail sequence.
|
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 |
#include <iostream> #include <string> #include <map> #include <vector> #include <cstdio> using namespace std; map<string,int> mp; map<int,string> pm; vector<string> vb[27]; int res[105]; int t,n; bool dfs(bool vis[],int v,int cnt) { if(cnt==n-1) { return 1; } string s=pm[v]; int idx=(s[s.size()-1]-'a')+1; // vis[v]=1; bool f=0; for(int i=0;i<vb[idx].size();i++) { s=vb[idx][i]; if(vis[mp[s]]==0) { vis[mp[s]]=1; res[cnt+1]=mp[s]; f=dfs(vis,mp[s],cnt+1); vis[mp[s]]=0; if(f) return 1; } } return 0; } int main() { //code bool vis[105]; scanf("%d",&t); string str; int idx; bool f; while(t--) { scanf("%d",&n); mp.clear(); pm.clear(); f=0; for(int i=1;i<27;i++) vb[i].clear(); for(int i=1;i<=n;i++) { cin>>str; mp[str]=i; pm[i]=str; vis[i]=0; idx=(str[0]-'a')+1; vb[idx].push_back(str); } for(int i=1;i<=n;i++) { if(vis[i]==0) { res[0]=i; vis[i]=1; f=dfs(vis,i,0); vis[i]=0; } if(f) break; } if(f) printf("Head to tail ordering is possible.\n"); else printf("Head to tail ordering is not possible.\n"); } return 0; } |