如何用c中的字符串中第二个最常见的字符替换字符串中最常见的字符？

Question

我写了一个C函数，从用户那里接收一个字符串，把出现频率最高的字母替换成字符串中出现频率第二高的字母。示例：对于输入 i love you more，将返回字符串 i levo yeu mero


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

void stringReplace(char str1[]);

int main()
{
    char str1[100] = { 0 };
    stringReplace(str1);
    return 0;
}

void stringReplace(char str1[])
{
    char ch1, ch2;
    int i, h, j, p, n, len, counter1 = 0, counter2 = 0, first, second, times;
    printf("Please enter the string - maximum = 100 characters:\n");
    printf("User input: ");
    fgets(str1, 100, stdin);
    str1[strcspn(str1, "\n")] = 0;
    len = strlen(str1);
    for (i = 0; i < len; i++) {
        counter1 = 0;
        for (j = 0; j < len; j++) {
            if (str1[i] == str1[j]) {
                counter1++;
            }
            if (counter1 > counter2) {
                first = i;
            }
        }
        counter2 = counter1;
    } //character which shows up most - found.

    counter2 = 0;

    for (p = 0; p < len; p++) {
        for (n = 0; n < len; n++) {
            if (str1[p] == str1[n]) {
                counter1++;
            }
            if (counter1 < first && counter1 > counter2) {
                second = p;
            }
        }
        counter2 = counter1;
    }

    ch1 = str1[first];
    ch2 = str1[second];
    
    for (h = 0; h < len; h++) {
        if (str1[h] == ch1) {
            str1[h] = ch2;
        }
    }
    puts(str1);
}

这是我完成的代码，它没有更改字符串，而是打印了相同的内容。例如：

Please enter the string - maximum = 100 characters:
User input: i love you more
i love you more

Answer 1

建议：使用辅助函数分而治之。

思考子问题：计算第 1 和第 2 最受欢迎的。

走字符串。在每个字符处计算它与字符串其余部分的出现次数。 O(n*n)

当检测到比第二名更好的计数时，调整第一名和第二名。

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

void most_popular2(const char *s, char pop[2]) {
  pop[0] = pop[1] = 0;
  size_t pop_count[2] = {0, 0};

  while (*s) {
    // Do not count white-space.
    if (!isspace(*(const unsigned char* )s)) {
      // How popular is *s?
      size_t count = 1;
      // sum all the matches on the rest of the string
      for (const char *r = s + 1; *r; r++) {
        if (*s == *r) {
          count++;
        }
      }

      // Test if better than the 2nd most popular.
      if (count > pop_count[1] && *s != pop[0]) {
        if (count > pop_count[0]) {
          // Demote 1st place to 2nd place.
          pop_count[1] = pop_count[0];
          pop[1] = pop[0];
          // Save new 1st place.
          pop_count[0] = count;
          pop[0] = *s;
        } else {
          // Save new 2nd place.
          pop_count[1] = count;
          pop[1] = *s;
        }

      }
    }
    s++;
  }
}

示例

int main() {
  char s[] = "i love you more i love you more\n";
  char pop[2];
  most_popular2(s, pop);
  printf("1st:%c 2nd:%c\n", pop[0], pop[1]);
}

输出

1st:o 2nd:e

将其留给 OP 来获取 2 个最受欢迎的字符并形成所需的输出。

更高效的代码可以复制字符串，将其排序为 O(n*(lng(n))，然后遍历它以找到最流行的 2 个。

Answer 2

感谢您的帮助，现在我明白了。这就是我所做的：

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

#define ASCII_A 97  // ascii for A is 97 
#define MAXSIZE 50 // max size for string 
#define ALPHABETS 26 //total number of alphabets 

//function declaration
void stringReplace(char s[], int a[]);

int main()
{
    //setting the string and the array of the alphabet
    char s[MAXSIZE] = {0};
    int a[ALPHABETS] = {0};

    //calling the function 
    stringReplace(s, a);
    return 0;
}
/*
function to replace the most common charcter with the second one
input: the string
output: none
*/
void stringReplace(char s[], int a[])
{
    int i;
    int max = 0, max2 = 0; 
    int len;
    char first_max, second_max;

    printf("Enter the string:\n"); 
    fgets(s, MAXSIZE, stdin);
    s[strcspn(s, "\n")] = 0;
    len = strlen(s);

    for(i=0; i<26; i++) // initialize all array elements to zero 
    {
        a[i]=0; 
    }       

    for(i=0; i<len; i++) // loop for traversing the string 
    {
        a[s[i]-ASCII_A]++; // increment by 1 for each occurrence. 
    }

    for(i=0; i< ALPHABETS; i++)
    {       
        if (a[i] > a[max])
        {
            max2 = max;
            max = i;
        }

        //If a[i] is in between max and max2 then update max2  //
        else if (a[i] > a[max2] && a[i] != a[max])
        {
            max2 = i;
        }
        first_max = ASCII_A+max;
        second_max = ASCII_A+max2;
    }
    //////////////////////////////////////////////////////////

    for (i = 0; i < len; i++) //replace the charcters
    {
       // check for first_max and replace
       if (s[i] == first_max)
       {
           s[i] = second_max;
       }

       // check for second_max and replace
       else if (s[i] == second_max)
       {
           s[i] = first_max;
       }
    }
    printf("Most common: %c\n",first_max );
    printf("Second most common: %c\n", second_max);
    printf("The new string is\n");
    puts(s);

}

如何用c中的字符串中第二个最常见的字符替换字符串中最常见的字符？

how to replace the most common character in a string with the second most common in the string in c?

c

arrays

string

integer

char