循環鏈表 - 無限循環

教我自己編程，我決定做一個簡單的瓦數計算器。每個州有不同的（平均）價格/ KWh。我的問題在代碼中啓動了第34行。 curr-> next不會爲空。循環鏈表 - 無限循環

我在做什麼錯？

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


float calculate(float w, float cents, float h); 

struct states 
{ 
    char *name; 
    char *price; 
    struct states *next; 
}; 

int main() 
{ 
    float watts,hours,cents; 
    int a = 0; 
    struct states *curr, dict[52]; 
    char st_ab[52][3] = {"ID","ND","WA","AR","UT","LA","WY","SD","NE","KY","WV","OK","OR","MT","MS","TN","IN","NC","MS","IA","KS","VA","NM","MN","SC","AZ","GA","AL","CO","OH","TX","IL","FL","NV","MI","WI","PA","MD","DC","DE","MA","RI","CA","ME","VT","NJ","NH","AK","CT","NY","HI"}; 
    char st_pr[52][5] = {"8.0","8.1","8.2","8.7","8.8","8.9","8.9","9.0","9.0","9.0","9.2","9.2","9.4","9.6","9.7","9.8","10.0","10.2","10.3","10.5","10.5","10.5","10.7","10.9","11.0","11.1","11.1","11.1","11.2","11.2","11.3","11.7","11.7","11.7","13.0","13.0","13.2","13.7","13.7","13.7","14.8","14.9","15.2","15.5","16.1","16.3","16.5","17.5","18.1","18.1","33.2"}; 
    char state[2]; 

    for(a=0;a<=52;a++) 
    { 
     memset(&dict[a],0,sizeof(struct states)); /* zero out structure */ 
     if(a==52) 
     { 
      break; /* if this is the last struct, leave it NULL so we can loop through linked list */ 
     } 
     dict[a].next=&dict[a+1];   
    } 

    for(curr = dict;curr ->next != NULL;curr = curr->next) /* fill our list with state abbr. and cost/KWh */ 
    { 
     curr->name = st_ab[a]; 
     curr->price = st_pr[a]; 
     a++; 
    } 

    puts("Dictionary loaded!"); 
    printf(" Two letter state code: ");     /* get info from user */ 
    scanf("%s",state); 

    printf(" Wattage of appliance: "); 
    scanf("%f",&watts); 

    printf(" Hours of use per day: "); 
    scanf("%f",&hours); 

    for(curr = dict; curr->next != NULL; curr=curr->next) 
    { 
     printf("comparing %s with %s\n", curr->name,state); /* search for our state, set cents respectively */ 
     if((strcmp(curr->name,state)) == 0) 
     { 
      printf("State found! -- %s\n",state); 
      cents=atof(curr->price); 
      printf("%f cents\n",cents); 
      break; 
     } else { 
      printf("state didn't match\n"); 
      continue; 
     } 
    } 

    printf("\nAverage cost per day: %.2f\n", calculate(watts,cents,hours)); 
    printf("Average cost per year: %.2f\n\n", (calculate(watts,cents,hours)) * 365);  

    return 0; 

} 

float calculate(float w, float c, float h) 
{ 
    float kwh = (w/1000) * h; 
    float cos = kwh*(c/100); 
    return(cos); 
}

來源

2013-03-28 elixxir

'for（a = 0; a <= 52; a ++）'最後一個有效索引是51. –

的問題是在

dict[a].next = &dict[a+1];

C標準保證&dict[a+1]是從未NULL，即使它是一個過去的陣列的端部。這會導致下一個循環經過列表的末尾，導致未定義的行爲（程序可能執行任何操作）。第一個循環後，做

dict[51].next = NULL;

結束鏈接列表。

編輯：與for(a=0;a<=52;a++)實際上你走過了數組末尾的兩個元素，所以行爲在兩個地方是未定義的。爲了解決這個問題，你需要循環到a<52。

來源

2013-03-28 14:43:57

非常感謝您的快速響應！經過一些其他小調整後，它現在工作非常好！ – elixxir

「curr->接下來就是從不爲空」 - 好了，你怎麼能指望你的for循環停止，如果你停止條件是curr->下次等於空？

來源

2013-03-28 14:43:43 SomeWittyUsername

循環鏈表 - 無限循環

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