00181.c (3377B)
1 /* example from http://barnyard.syr.edu/quickies/hanoi.c */ 2 3 /* hanoi.c: solves the tower of hanoi problem. (Programming exercise.) */ 4 /* By Terry R. McConnell (12/2/97) */ 5 /* Compile: cc -o hanoi hanoi.c */ 6 7 /* This program does no error checking. But then, if it's right, 8 it's right ... right ? */ 9 10 11 /* The original towers of hanoi problem seems to have been originally posed 12 by one M. Claus in 1883. There is a popular legend that goes along with 13 it that has been often repeated and paraphrased. It goes something like this: 14 In the great temple at Benares there are 3 golden spikes. On one of them, 15 God placed 64 disks increasing in size from bottom to top, at the beginning 16 of time. Since then, and to this day, the priest on duty constantly transfers 17 disks, one at a time, in such a way that no larger disk is ever put on top 18 of a smaller one. When the disks have been transferred entirely to another 19 spike the Universe will come to an end in a large thunderclap. 20 21 This paraphrases the original legend due to DeParville, La Nature, Paris 1884, 22 Part I, 285-286. For this and further information see: Mathematical 23 Recreations & Essays, W.W. Rouse Ball, MacMillan, NewYork, 11th Ed. 1967, 24 303-305. 25 * 26 * 27 */ 28 29 #include <stdio.h> 30 #include <stdlib.h> 31 32 #define TRUE 1 33 #define FALSE 0 34 35 /* This is the number of "disks" on tower A initially. Taken to be 64 in the 36 * legend. The number of moves required, in general, is 2^N - 1. For N = 64, 37 * this is 18,446,744,073,709,551,615 */ 38 #define N 4 39 40 /* These are the three towers. For example if the state of A is 0,1,3,4, that 41 * means that there are three discs on A of sizes 1, 3, and 4. (Think of right 42 * as being the "down" direction.) */ 43 int A[N], B[N], C[N]; 44 45 void Hanoi(int,int*,int*,int*); 46 47 /* Print the current configuration of A, B, and C to the screen */ 48 void PrintAll() 49 { 50 int i; 51 52 printf("A: "); 53 for(i=0;i<N;i++)printf(" %d ",A[i]); 54 printf("\n"); 55 56 printf("B: "); 57 for(i=0;i<N;i++)printf(" %d ",B[i]); 58 printf("\n"); 59 60 printf("C: "); 61 for(i=0;i<N;i++)printf(" %d ",C[i]); 62 printf("\n"); 63 printf("------------------------------------------\n"); 64 return; 65 } 66 67 /* Move the leftmost nonzero element of source to dest, leave behind 0. */ 68 /* Returns the value moved (not used.) */ 69 int Move(int *source, int *dest) 70 { 71 int i = 0, j = 0; 72 73 while (i<N && (source[i])==0) i++; 74 while (j<N && (dest[j])==0) j++; 75 76 dest[j-1] = source[i]; 77 source[i] = 0; 78 PrintAll(); /* Print configuration after each move. */ 79 return dest[j-1]; 80 } 81 82 83 /* Moves first n nonzero numbers from source to dest using the rules of Hanoi. 84 Calls itself recursively. 85 */ 86 void Hanoi(int n,int *source, int *dest, int *spare) 87 { 88 int i; 89 if(n==1){ 90 Move(source,dest); 91 return; 92 } 93 94 Hanoi(n-1,source,spare,dest); 95 Move(source,dest); 96 Hanoi(n-1,spare,dest,source); 97 return; 98 } 99 100 int main() 101 { 102 int i; 103 104 /* initialize the towers */ 105 for(i=0;i<N;i++)A[i]=i+1; 106 for(i=0;i<N;i++)B[i]=0; 107 for(i=0;i<N;i++)C[i]=0; 108 109 printf("Solution of Tower of Hanoi Problem with %d Disks\n\n",N); 110 111 /* Print the starting state */ 112 printf("Starting state:\n"); 113 PrintAll(); 114 printf("\n\nSubsequent states:\n\n"); 115 116 /* Do it! Use A = Source, B = Destination, C = Spare */ 117 Hanoi(N,A,B,C); 118 119 return 0; 120 } 121 122 /* vim: set expandtab ts=4 sw=3 sts=3 tw=80 :*/