Permutations by swapping: Difference between revisions
Added C implementation.
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</pre>
=={{header|C}}==
Implementation of Heap's Algorithm, array length has to be passed as a parameter for non character arrays, as sizeof() will not give correct results when malloc is used. Prints usage on incorrect invocation.
<lang C>
/*Abhishek Ghosh, 25th October 2017*/
#include<stdlib.h>
#include<string.h>
#include<stdio.h>
int flag = 1;
void heapPermute(int n, int arr[],int arrLen){
int temp;
int i;
if(n==1){
printf("\n[");
for(i=0;i<arrLen;i++)
printf("%d,",arr[i]);
printf("\b] Sign : %d",flag);
flag*=-1;
}
else{
for(i=0;i<n-1;i++){
heapPermute(n-1,arr,arrLen);
if(n%2==0){
temp = arr[i];
arr[i] = arr[n-1];
arr[n-1] = temp;
}
else{
temp = arr[0];
arr[0] = arr[n-1];
arr[n-1] = temp;
}
}
heapPermute(n-1,arr,arrLen);
}
}
int main(int argC,char* argV[0])
{
int *arr, i=0, count = 1;
char* token;
if(argC==1)
printf("Usage : %s <comma separated list of integers>",argV[0]);
else{
while(argV[1][i]!=00){
if(argV[1][i++]==',')
count++;
}
arr = (int*)malloc(count*sizeof(int));
i = 0;
token = strtok(argV[1],",");
while(token!=NULL){
arr[i++] = atoi(token);
token = strtok(NULL,",");
}
heapPermute(i,arr,count);
}
return 0;
}
</lang>
Output:
<pre>
C:\rosettaCode>heapPermute.exe 1,2,3
[1,2,3] Sign : 1
[2,1,3] Sign : -1
[3,1,2] Sign : 1
[1,3,2] Sign : -1
[2,3,1] Sign : 1
[3,2,1] Sign : -1
</pre>
=={{header|C++}}==
Direct implementation of Johnson-Trotter algorithm from the reference link.
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