使用C中的指针反转字符串的程序 [英] Program to reverse a string using pointers in C

问题描述

你好伙计们我​​试图通过从函数返回指向char的指针来反转字符串的程序



我试过的：

hello guys i am trying to make c program for reversing the string by returning the pointer to char from the function

What I have tried:

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

char* reversestring(char* input);
int main()
{
	int i;
	char* output;
	char inputstring[100];
	printf("enter the string\n");
	gets(inputstring);
	output = reversestring(inputstring);

i希望以两种方式打印相同的字符串，即使用printf和运行循环请建议我双向打印在相同的程序



这里我已经采取i = 0到4的固定字符串在这里假设用户将输入长度为5字符的固定字符串，因为我不知道正确的方法

i want to print the same string in both way that is by using printf and by running the loop please suggest me both way to print in same program

here i have taken i=0 to 4 for fixed string here i m assuming that user will enter a fixed string of length 5 char because i dont know the proper way

	printf("%s\n",output);
	for(i=0;i<4;i++) {
		printf("%c",(output+i));
	}
}

从这里开始反转功能

reverse function start from here

char* reversestring(char* input)
{
    int count=0,begin,end;

	char* output=(char*) malloc(100);
	while(*input!=0) {
		count++;
	}

	end=count-1;

	for(begin=0;begin<count;begin++) {
		*(output+begin)=*(input+end);
		 end--;
	}

	output[begin]='\0';
	return output;
}

没有错误并警告它输入的只是没有给出输出（光标闪烁只有程序没有结束）

there is no error and warning it is taking input only not giving the output(cursor is blinking only program is not ending)

推荐答案

这个循环不会完成：

This loop won't finish:

while(*input!=0) {
    count++;
}

您可以将其替换为：

You could replace it with:

while (*(input + count) != 0) {
    count++;
}

要按字符打印反向字符串，请使用strlen [ ^ ]：

To print your reversed string character by character, use strlen[^]:

for (int i = 0; i<strlen(output); i++) {
    printf("%c", *(output + i));
}

在我看来，内存分配应该是来电者责任。此外，永远不要使用获取功能。

尝试

In my opinion the memory allocation should be caller responsibility. Moreover, never ever use gets function.
Try

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

char * reverse( char * rev, const char *  str, size_t length )
{
  size_t n;
  for (n=0; n<length; ++n)
  {
    rev[n] = str[length-1-n];
  }
  rev[n] ='\0';
  return rev;
}

int main()
{
  char s[100];
  printf("please enter the string:\n");

  if ( ! fgets( s, sizeof(s), stdin) ) return -1;

  size_t length = strlen(s);

  char * r = (char *) malloc( length+1 );
  if ( ! r ) return -2;

  reverse( r, s, length);

  printf("reversed: %s\n", r);

  free(r);
  return 0;
}

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