获取有关“间接级别不同”的错误答案

【问题标题】：Getting error about "differs in level of indirection"获取有关“间接级别不同”的错误
【发布时间】：2022-01-16 09:29:26
【问题描述】：

您好，我刚刚完成了我的项目的编码，但是当我尝试编译时，我一直收到此错误。哪个是'<=': 'int' differs in levels of indirection from 'int *'，我不知道发生了什么，我已经检查了指针并在定义变量类型时已经将其放入，但仍然无法安全编译。


    #define _CRT_SECURE_NO_WARNINGS
/* C Program to find Shortest Distances or Path */

#include<stdio.h>
#define WORD 200

int main(void) {
    int path, point = 1;
    int* ncity[WORD];
    char* cityname[WORD][WORD];
    float distance[WORD][WORD];
    float total[WORD];

    printf("This program will input 5 path and calculates the minimum between KL Sentral, KL & Jurong East, Singapore");
    printf("\n\t\t-------------------------------------------------------------");
    printf("\n\t\tMinimum Path between KL Sentral, KL & Jurong East, Singapore");
    printf("\n\t\t-------------------------------------------------------------");

    printf("\nPlease enter the total path that you want to calculate: ");
    scanf("%d", &path);

    for (int i = 1; i <= path; i++) {
        printf("\n\n----Path %d----", i);
        printf("\nState the number of city that the path cross: ");
        scanf("%d", ncity[i]);
        for (int x = 1; x <= path; x++) {
            for (int y = 1; y <= ncity[i]; y++) {
                printf("\nCity %d named : ", y);
                scanf("%s", &cityname[x][y]);
                printf("\nEnter the distance to the city %d: ", y);
                scanf("%f", &distance[x][y]);
                total[x] = +distance[x][y];
            }
        }
    }
    //Find the minimum path
    for (int x = 1; x <= path; x++) {
        if (total[x] < total[point]) {
            point = x;
        }
    }
    printf("\nThe minimum path between KL Sentral, Kuala Lumpur & Jurong East, Singapore");
    printf("\nPath: Path %d", point);
    printf("\nTotal Distance: %f", total[point]);
    printf("\n\t\tCity Name");
    //Loop for 42
    for (int z = 1; z <= ncity[point]; z++) {
        for (int x = 1; x <= path; x++) {
            for (int y = 1; y <= ncity; y++) {
                printf("\n\t\t %s", cityname[x][y]);
                printf("\n\t\t %f km", distance[x][y]);
            }
        }
    }
}

This the error that had been listed once i started compiling my code

【问题讨论】：

ncity[i] 是一个指针。它的类型是int *，您在这里将它与int 类型进行比较 - for (int y = 1; y <= ncity[i]; y++)。
在索引数组时要小心循环变量范围。在这种情况下，它们几乎总是应该从0 开始而不是1，并以< limit 而不是<= limit 结束。
旁白：请养成输出换行符last而不是first的习惯。

标签： arrays c pointers

【解决方案1】：

通过在循环中使用z <= ncity[point]，您可以将“z”与存储ncity[pointer] 值的地址的实际编号进行比较。通常它是一个很大的“int”值。我不明白为什么你需要一个指针数组，但要获得ncity[point] 的第一个值，你需要取消引用：*ncity[pointer]。在您的第三个循环中发生了同样的情况：y <= ncity。您将“y”变量与ncity 变量的地址数进行比较。再次，相当大的数字，所以很可能 'y' 变量将在 'cityname' 和 'distance' 之外，然后你会得到 'segmentation fault' 错误。要获得“ncity”的整个大小，您需要遍历所有值或仅在第三个循环中使用 path valiable

for (int y = 1; y <= path; y++) {
  printf("\n\t\t %s", cityname[x][y]);
  printf("\n\t\t %f km", distance[x][y]);
}

【讨论】：