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POmergesort array of int using pointers
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copied!<p>For school I have to program a merge sort using only pointers. I've tried almost everything, but I can not get it working.</p> <pre><code>#include <stdio.h> #include <stdlib.h> #include <string.h> #define num_elementi(array) (sizeof(array)/sizeof(array[0])) void selsort(int arr[],int n); void swap(int * a, int * b); void print(int arr[],int n); void insort(int arr[],int n); void mergesort(int arr[],int *p,int *u); void merge(int arr[],int * p, int * q,int * u); int main(int argc, char *argv[]){ int arr[]={99,12,14,65,2,7,54,78,5,1,43,59,88,28,61}; int n=num_elementi(arr); printf("numero elementi array: %d\n",n); print(arr,n); printf("numero elementi array: %d\n",n); mergesort(arr,&arr[0],&arr[n-1]); print(arr,n); system("pause"); } void selsort(int arr[],int n){ int *i,*j; for(i=arr;i<&arr[n-1];i++){ for(j=i+1;j<&arr[n];j++){ if(*j<*i)swap(i,j);; } } } void swap(int * a, int * b){ int temp; temp=*a; *a=*b; *b=temp; } void print(int arr[],int n){ int * p=arr; for(p;p<&arr[n];p++)printf("%d ",*p); printf("\n"); } void insort(int arr[],int n){ int *i,*k; for(i=&arr[1];i<&arr[n];i++){ k=i-1; while(k>=&arr[0]&& *k>*(k+1)){ swap(k,k+1); k=k-1; } } } void mergesort(int arr[],int *p,int *u){ if (p<u){ int *q=((u-p)/2)+p; mergesort(arr,p,q); mergesort(arr,q,u-1); merge(arr,p,q,u); } } void merge(int arr[],int * p, int * q,int * u){ int arr1[u-p]; //inizializzazione array di dimensioni utili int * i=p; //puntatore al primo elemento di arr int *j=q+1; //puntatore al elemento di mezzo +1 di arr int *k= arr1; //puntatore al primo elemento di arr1 if (u-p==1){ if (*u<*p){ swap(u,p); } return; } while(i<q && j<u){ if(*i<*j){ *k=*i; i=i+1; } else{ *k=*j; j=j+1; } k=k+1; } while(i<q){*k=*i;i++;k++;} while(j<u){*k=*j;j++;k++;} i=p; k=arr1; for(i,k;i<&arr[u-p];i++,k++){ *i=*k; } } </code></pre> <p>Can someone please explain what I did wrong? Thank you so much!!</p> <p>PS: Please forgive my really bad English.</p> <p><strong><em>EDIT</em></strong> new code for the suggestion of Maciej Hehl</p> <pre><code>#include <stdio.h> #include <stdlib.h> #include <string.h> #define num_elementi(array) (sizeof(array)/sizeof(array[0])) void swap(int * a, int * b); void print(int arr[],int n); void mergesort(int arr[],int * arr_begin,int * arr_end); void merge(int * destination, int * r1_begin, int * r1_end, int * r2_begin, int * r2_end); int main(int argc, char *argv[]){ int arr[]={99,12,14,65,2,7,54,78,5,1,43,59,88,28,61}; int n=num_elementi(arr); print(arr,n); mergesort(arr,&arr[0],&arr[n-1]); print(arr,n); system("pause"); } void swap(int * a, int * b){ int temp; temp=*a; *a=*b; *b=temp; } void print(int arr[],int n){ int * p=arr; for(p;p<&arr[n];p++)printf("%d ",*p); printf("\n"); } void mergesort(int arr[],int * arr_begin,int * arr_end){ int * med,*arr1,*p,*p1; printf("i'm doing something\n"); if(arr_begin<arr_end){ med=arr[arr_end-arr_begin]/2+arr_begin; mergesort(arr,arr_begin,med); mergesort(arr,med+1,arr_end); arr1=malloc((arr_end-arr_begin)*sizeof(int)); printf("msort calls ended begin merge\n"); merge(arr1,arr_begin,med,med+1,arr_end); for(p=arr,p1=arr1;p<arr_end&&p1<&arr1[arr_end-arr_begin];p++,p1++){ *p=*p1; } } } void merge(int * destination, int * r1_begin, int * r1_end, int * r2_begin, int * r2_end){ int *pdest=destination; if (r1_end-r1_begin==1){ if (*r1_end<*r1_begin){ swap(r1_end,r1_begin); } return; } if (r2_end-r2_begin==1){ if (*r2_end<*r2_begin){ swap(r2_end,r2_begin); } return; } while(r1_begin<=r1_end&&r2_begin<=r2_end){ if(*r1_begin<*r2_begin){ *pdest=*r1_begin; r1_begin++; } else{ *pdest=*r2_begin; r2_begin++; } pdest++; } while(r1_begin<r1_end){ *pdest=*r1_begin; r1_begin++;pdest++; } while(r2_begin<r2_end){ *pdest=*r2_begin; r2_begin++;pdest++; } } </code></pre>

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