可變大小的數組結構

Question

我想將數據保存在名爲plist的數組中。這些陣列的大小可能不同，並且是名爲ParticleList的結構的一部分。我知道如何創建一個大小爲n[0]的列表。例如n[0]的大小爲2.因此，大小爲2的列表。但是，如果我想創建多個大小爲n[0], n[1], n[2]的ParticleList類型的列表，我該怎麼辦？

爲了削減長話短說：我應該如何修改我的代碼，以訪問可變大小的列表不知何故像pl[numberOfList].plist[PositionInArray] = -1或`PL [numberOfList] - >的plist [PositionInArray] = -1'

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

typedef struct{ 
    double *plist; 
    int plistSize; 
} ParticleList; 

void sendPar(int *n, int nl){ 

    // Allocate memory for struct ParticleList 
    ParticleList *pl = malloc(sizeof(ParticleList)); 

    // Allocate memory for list 
    pl->plist = malloc(sizeof(double)*n[0]); 

    // Fill list with data 
    for(int k=0; k<n[0]; k++){ 
     pl->plist[k] = -1; 
    } 
    // Write size of list into file 
    pl->plistSize = n[0]; 

    // Print data 
    printf("Content of list:\n"); 
    for(int k=0; k<n[0]; k++){ 
     printf("%lf\n", pl->plist[k]); 
    } 
    printf("Size of list: %d\n", pl->plistSize); 


    // Free memory 
    free(pl); 
} 

int main(){ 
    // Number of lists 
    int nl = 3; 

    // Size of lists 
    int n[nl]; 
    n[0] = 2; 
    n[1] = 3; 
    n[2] = 4; 

    sendPar(n, nl); 
} 

Answer 1

你的意思是這樣的嗎？

typedef struct{ 
    int plistSize; 
    double* plist; 
} ParticleList; 

int main() 
{ 
    int i, z = 0; 

    /* Assuming you have three lists with three different sizes */ 
    double list1[2] = {-1.0, -1.1}; 
    double list2[3] = {-2.0, -2.1, -2.2}; 
    double list3[4] = {-3.0, -3.1, -3.2, -3.3}; 

    /* Create an array of three Particle Lists */ 
    ParticleList pl[3] = {{list1, 2},{list2, 3},{list3, 4}}; 

    /* Access the values in the Particle Lists */ 
    for(i = 0; i < 3; i++) 
    { 
     printf("ParticleList pl[%i]:\n", i); 

     for(z = 0; z < pl[i].plistSize; z++) 
     { 
      printf("pl[%i].plist[%i] = %f\n", i, z, pl[i].plist[z]); 
     } 
    } 

    /* Change the first item of the second list */ 
    pl[1].plist[0] = 2.3;   
} 

這樣你可以在每個列表中

pl[<index of list>].plist[<index of list item>]

更加動感有點用靈活的數組成員（這樣的名單可以被另一個取代訪問每個項目不同大小的列表）：

注意我改變了struct！

typedef struct{ 
    int plistSize; 
    double plist[]; 
} ParticleList; 

int main() 
{ 
    int i, z = 0; 
    ParticleList *pl[3]; 

    /* Allocate memory for the lists */ 
    pl[0] = malloc(sizeof(ParticleList) + sizeof(double[2])); 
    pl[0]->plistSize = 2; 
    pl[1] = malloc(sizeof(ParticleList) + sizeof(double[3])); 
    pl[1]->plistSize = 3; 
    pl[2] = malloc(sizeof(ParticleList) + sizeof(double[4])); 
    pl[2]->plistSize = 4; 

    /* Write the values in the Particle Lists */ 
    for(i = 0; i < 3; i++) 
    { 
     printf("ParticleList pl[%i]:\n", i); 

     for(z = 0; z < pl[i]->plistSize; z++) 
     { 
      pl[i]->plist[z] = -i; 
     } 
    } 

    /* Print the values */ 
    for(i = 0; i < 3; i++) 
    { 
     printf("ParticleList pl[%i]:\n", i); 

     for(z = 0; z < pl[i]->plistSize; z++) 
     { 
      printf("pl[%i]->plist[%i] = %f\n", i, z, pl[i]->plist[z]); 
     } 
    } 

    /* Change the first value of the second list */ 
    pl[1]->plist[0] = -1.1; 

    /* Replace the first list by a new one */ 
    free(pl[0]); 
    pl[0] = malloc(sizeof(ParticleList) + sizeof(double[5])); 
    pl[0]->plistSize = 5; 

    /* Assign some new values to the new list 1 */ 
    pl[0]->plist[0] = -4.1; 
    pl[0]->plist[1] = -4.2; 
    pl[0]->plist[2] = -4.3; 
    pl[0]->plist[3] = -4.4; 
    pl[0]->plist[4] = -4.5; 

    /* Print the values */ 
    for(i = 0; i < 3; i++) 
    { 
     printf("ParticleList pl[%i]:\n", i); 

     for(z = 0; z < pl[i]->plistSize; z++) 
     { 
      printf("pl[%i]->plist[%i] = %f\n", i, z, pl[i]->plist[z]); 
     } 
    } 

    /* free all lists before exiting the program */ 
    for(i = 0; i < 3; i++) 
    { 
     free(pl[i]); 
    } 

    return 0; 
} 

Answer 2

看起來您正在尋找稱爲靈活陣列成員的語言功能。它的工作原理是這樣的：

typedef struct{ 
    int plistSize; 
    double plist[]; 
} ParticleList; 

ParticleList *pl = malloc(sizeof(ParticleList) + sizeof(double[n])); 
pl->plistSize = n; 
... 
free(pl); 

哪裏n是你想要plist有大小。