Search Algorithm Little Exercise

1. All permutations of the first n natural numbers:

1#include <iostream>2#include <cstdio>3#include <cstring>4 5 using namespacestd;6 7 intCount=1, N;8 BOOL*b;9 int*A;Ten  One voidDfsint); A  - intMain () - { thescanf"%d",&n); -b=New BOOL[n+1]; -A=New int[n+1]; -memset (b,0, n+1);//We can't write sizeof (b), B is a variable pointer +Dfs1); -     return 0; + } A voidDfsintt) at { -      for(intI=1; i<=n;i++) -     { -         if(B[i])Continue; -b[i]=1; -a[t]=i; in         if(t==N) -         { toprintf"%d", count++); +              for(intj=1; j<=n;j++) printf ("%d", A[j]); -Puts""); theb[i]=0; *             return; $         }Panax NotoginsengDFS (t+1); -b[i]=0; the     } +}

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2. Whether the maze has access (DFS):

1#include <iostream>2#include <cstdio>3#include <cstring>4 5 using namespacestd;6 7 Const intn= -;8 CharMi_gong[n][n];9 BOOLB[n][n];Ten intdx[]={1,-1,0,0},dy[]={0,0,1,-1}; One intN,m,x1,x2,y1,y2; A BOOLBB; -  - voidCreate (); the BOOLCanmove (intXinty); - voidDfs (intXintYintstep); -  - intMain () + { - Create (); +Dfs (X1,y1,0); A     if(bb==0) puts ("The little mouse couldn't get out and was choked to death. "); at     return 0; - } - voidCreate () - { -Puts"Enter the number of rows in the maze and the start and end point of the mouse, and then enter the maze for each lattice point. Representative can go, #代表不可以走. "); -scanf"%d%d%d%d%d%d",&n,&m,&x1,&y1,&x2,&y2); in      for(intI=1; i<=n;i++) -     { to GetChar (); +          for(intj=1; j<=m;j++) -         { thescanf"%c",&mi_gong[i][j]); *         } $     }Panax Notoginseng } - BOOLCanmove (intXinty) the { +     returnX>0&&x<=n&&y>0&&y<=m&&mi_gong[x][y]=='.'&&b[x][y]==0; A } the voidDfs (intXintYintStep) + { -     if(BB)return; $     if(x==x2&&y==y2) $     { -Puts"The little mouse can get out of the maze. "); -bb=1; the         return; -     }Wuyi     intTx,ty; theb[x][y]=1; -      for(intI=0;i<4; i++) Wu     { -tx=x+Dx[i]; Aboutty=y+Dy[i]; $         if(Canmove (Tx,ty)) Dfs (tx,ty,step+1); -     } -b[x][y]=0; -}

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3. Given n positive integers a1,a2,a3,..., an, and a positive integer k, ask whether it is possible to select several numbers from the n number to make it and K:

1#include <iostream>2#include <cstdio>3#include <cstring>4 5 using namespacestd;6 7 BOOLans;8 intn,k,*a,*s;9 voidDfsintIintsum);Ten  One intMain () A { -scanf"%d%d",&n,&k); -A=New int[n]; thes=New int[n]; -      for(intI=0; i<n;i++) scanf ("%d",&a[i]); -     ints0=0; -      for(inti=n-1; i>=0; i--) s0+=a[i],s[i]=S0; +Dfs0,0); -     if(ANS) cout<<"true"; +     return 0; A } at voidDfsintIintsum) - { -     if(ans| | sum>k| | SUM+S[I]&LT;K)return; -     if(i==N) -     { -         if(sum==k) ans=true; in         return; -     } toDFS (i+1, sum+a[i]); +DFS (i+1, sum); -}

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Search Algorithm Little Exercise