C：如何刪除一維數組中的相鄰副本？

Question

說我有一個數組：

int {2, 2, 2, 6, 6, 2, 2, 5, 5, 5} 

，我想刪除所有相鄰重複，使之成爲

int {2, 6, 2, 5} 

我怎樣才能做到這一點？

Answer 1

不知道你試過了什麼。我的想法是這樣的。

int i, num[] = {2, 2, 2, 6, 6, 2, 2, 5, 5, 5}; 

// Prepare new array for the result (result never larger than num[]) 
int *newNum = malloc(sizeof(num)); 
int used = 0, last = 0; 

// Get number of elements in num[], which is 10 in this example 
size_t n = sizeof(num)/sizeof(int); 

for (i = 0; i < n; i++) 
{ 
    if (num[i] != last) 
    { 
     newNum[used++] = num[i]; 
    } 
    last = num[i]; 
} 

printf("new array: \n"); 
for (i = 0; i < used; i++) 
{ 
    printf("%i ", newNum[i]); 
} 

Answer 2

這樣的：

#include <stdio.h> 
#include <stdlib.h> 
#include <string.h> 

int main(void){ 
    int size = 10; 
    int *array = memcpy(malloc(size * sizeof(*array)), (int[]){2, 2, 2, 6, 6, 2, 2, 5, 5, 5}, size * sizeof(*array)); 
    int i, new_size; 

    for(i = new_size = 1; i < size; ++i){ 
     if(array[new_size-1] != array[i]) 
      array[new_size++] = array[i]; 
    } 
    if(size > new_size){ 
     size = new_size; 
     array = realloc(array, size * sizeof(*array)); 
    } 
    for(i = 0; i < size; ++i) 
     printf("%d ", array[i]);//2 6 2 5 

    free(array); 
    return 0; 
}