June 2018 Update

Task/Permutations-by-swapping/C/permutations-by-swapping.c

@@ -0,0 +1,69 @@
+/*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;
+}