一波C语言字符数组实用技巧集锦

字符数组倒序

#include <stdio.h> 

 void daoxu(char str[]){
   int i;
   char temp;
   for(i = 0; i < strlen(str) / 2 ; i ++){
     temp = str[i];
     str[i] = str[strlen(str) - i-1];
     str[strlen(str) - i-1] = temp;
   }
 }

单词计数   

 int wordCount(char str[]){
   int i;
   int count = 0;
   int word = 0;
   for (i = 0 ; str[i] != '\0' ; i ++)
   {
     if (str[i] == ' ')
     {
       word = 0;
     }else if (word == 0)
     {
       word = 1;
       count ++;
     }
   }
   return count;
 }

字符大写转小写

 void mylwr(char str[]){
   int i;
   for (i = 0 ; str[i] != '\0' ; i ++)
   {
     if (str[i] >= 'A' && str[i] <= 'Z')
     {
       str[i] += 'a' - 'A';
     }
   }
 } 

字符小写转大写

 void myupr(char str[]){
   int i;
   for (i = 0 ; str[i] != '\0' ; i ++)
   {
     if (str[i] >= 'a' && str[i] <= 'z')
     {
       str[i] -= 'a' - 'A';
     }
   }
 }

字符数组计算字符串长度   

 int mylen(char str[]){
   int len;
   for (len = 0 ; str[len] != '\0' ; len ++);
   return len;
 }

字符串连接 

 void mycat(char str1[],char str2[]){
   int i,j;
   for (i = 0 ; str1[i] != '\0' ;i++);
   for (j = 0 ; str2[j] != '\0' ; j ++)
   {
     str1[i + j] = str2[j];
   }
   str1[i + j] = '\0';
 }

指定长度串接 

void myncat(char str1[],char str2[], int len){
   int i,j;
   for(i = 0; str1[i] != '\0'; i++);
   for (j = 0; j < len; j++)
   {
     str1[i + j] = str2[j];
   }
   str1[i + j] = '\0';
 }

字符数组拷贝     

 void mycpy(char dst[],char src[]){
   int i = 0;
   do
   {
     dst[i] = src[i];
   } while (src[i++] != '\0');
 }

字符数组指定长度拷贝     

 void myncpy(char dst[],char src[], int len){
   int i;
   for (i = 0; i < len; i++)
   {
     dst[i] = src[i];
   }
   dst[i] = '\0';
 }

找出句子中最长的单词 

 void longest(char dst[],char src[]){
   int i = 0,j;
   int count =0;
   int max = -1;
   do
   {
     if (src[i] ==' ' || src[i] == '\0')
     {
       if (count > max)
       {
         max = count;
         for (j = 0; j < count; j++)
         {
           dst[j] = src[i - count + j];
         }
         dst[j] = '\0';
       }
       count = 0;
     }else{
       count++;
     }
   } while (src[i++] != '\0');
 }

从字符串中提取整形数字

#include <stdio.h> 

int getint(char str[], int a[]){//从字符串中提取数字并放在数组中
  int i = 0;
  int w = 0;
  int c = 0;
  int j, k;
  do
  {
    if (str[i] > '0' && str[i] <= '9')
    {
      w++;
    }else if (w)
    {
      j = 0;
      for (k = w; k > 0; k--)
      {
        j *= 10;
        j += str[i - k] - '0';
      }
      w = 0;
      a[c] = j;
      c++;
    }
  } while (str[i++] != '\0');
  return c;
} 

void main(){
  char str[100];
  int a[100];
  int i, j;
  gets(str);
  i = getint(str,a);
  for (j = 0; j < i; j++)
  {
    printf("%d ",a[j]);
  }
}

整形、字符数组型转换

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

int sumof1(int x)//求一个数转换成二进制以后1的个数
{
  int countx = 0;
  while(x)
  {
    countx ++;
    x &= x-1; //每位与一次x - 1；就能消掉最后一个1
  }
  return countx;
} 

void main(){ 

  char c[10];
  int i = 999; 

  itoa(i, c, 10);//以10进制转换成字符数组
  puts(c); 

  itoa(i, c, 16);//以16进制转换成字符数组
  printf("0x%s\n", c); 

  itoa(i, c, 8);//以8进制转换成字符数组
  printf("0%s\n", c); 

  itoa(i, c, 2);//以2进制转换成字符数组
  puts(c); 

  i = atoi(c);//再将字符串转成整形
  printf("%d\n", i); 

  printf("%d\n", sumof1(i));//以2进制表示时1的个数
}