#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; 
   } 
 }

單詞計數(shù)

 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; 
 }

字符大寫轉小寫

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

字符小寫轉大寫

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

字符數(shù)組計算字符串長度

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

字符串連接

 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'; 
 }

指定長度串接

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'; 
 }

字符數(shù)組拷貝

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

字符數(shù)組指定長度拷貝

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

找出句子中最長的單詞

 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'); 
 }

從字符串中提取整形數(shù)字

#include <stdio.h> 
 
int getint(char str[], int a[]){//從字符串中提取數(shù)字并放在數(shù)組中 
  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、字符數(shù)組型轉換

#include <stdio.h> 
#include <stdlib.h> 
 
int sumof1(int x)//求一個數(shù)轉換成二進制以后1的個數(shù) 
{ 
  int countx = 0; 
  while(x) 
  { 
    countx ++; 
    x &= x-1; //每位與一次x - 1；就能消掉最后一個1 
  } 
  return countx; 
} 
 
void main(){ 
 
  char c[10]; 
  int i = 999; 
 
  itoa(i, c, 10);//以10進制轉換成字符數(shù)組 
  puts(c); 
 
  itoa(i, c, 16);//以16進制轉換成字符數(shù)組 
  printf("0x%s\n", c); 
 
  itoa(i, c, 8);//以8進制轉換成字符數(shù)組 
  printf("0%s\n", c); 
 
  itoa(i, c, 2);//以2進制轉換成字符數(shù)組 
  puts(c); 
 
  i = atoi(c);//再將字符串轉成整形 
  printf("%d\n", i); 
 
  printf("%d\n", sumof1(i));//以2進制表示時1的個數(shù) 
}

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