Question

在下面的代码中，该函数返回一个char指针“ p”，并存储在也是一个指针的“ out”变量中。当我尝试使用printf语句进行打印时，它不会向控制台输出任何内容，是否有指针？

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

char * longestCommonPrefix(char **strs, int strsSize){
    int j = 0;
    char *p;
    char result[10];
    int len = strlen(result);
    while(j < strlen(strs[0])){
        if(strs[0][j] == strs[1][j] && strs[1][j] == strs[2][j]){
            result[len++] = strs[0][j];
        }
        j++;
    }
    result[len] = '\0';
    p = result;
    return p;
}

int main()
{
    char *arr[] = {"flower", "flow", "flight"};
    char **ptr; 
    char *out;
    int size = sizeof(arr) / sizeof(arr[0]);
    ptr = arr;
    out = longestCommonPrefix(ptr, size);//breakpoint here shows the expected output
    printf("%s", out); //does not print the output to console
}

Answer 1

感谢@Paul Ogilvie，我能够通过在堆中动态分配内存，strcpy到指针并返回指针来解决该问题，因为当时我正在打印，因为本地内存当时不存在。

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

char * longestCommonPrefix(char **strs, int strsSize){
    int j = 0;
    char* p = malloc(10 * sizeof *p);
    char result[10];
    int len = strlen(result);
    while(j < strlen(strs[0])){
        if(strs[0][j] == strs[1][j] && strs[1][j] == strs[2][j]){
            result[len++] = strs[0][j];
        }
        j++;
    }
    result[len] = '\0';
    strcpy(p, result);
    return p;
}

int main()
{
    char *arr[] = {"flower", "flow", "flight"};
    char **ptr;
    int size = sizeof(arr) / sizeof(arr[0]);
    ptr = arr;
    char *out = longestCommonPrefix(ptr, size);
    printf("%s\n", out);
    free(out);
}

longestCommonPrefix从函数返回但未打印到C的控制台

1 个答案: