New Code Day15

1.一个数组中只有两个数字是出现一次， 其他所有数字都出现了两次。 找出这两个数字，编程实现。

#define _CRT_SECURE_NO_WARNINGS 1#include <stdio.h>
#include <assert.h>void find_num(int *arr,int len)
{int flag;int i = 0,j = 0;assert(arr);for(i=0; i<len; i++){flag = 1;for(j=0; j<len; j++){if(i == j)j++;else if(arr[i] == arr[j])flag = 2;}if(1 == flag){printf("%d ",arr[i]);}}}int main()
{int arr[] = {1,2,3,4,5,6,5,4,3,2,1,7};int len = sizeof(arr)/sizeof(arr[0]);find_num(arr,len);return 0;
}

2.喝汽水，1瓶汽水1元，2个空瓶可以换一瓶汽水， 给20元，可以多少汽水。 编程实现。

#define _CRT_SECURE_NO_WARNINGS 1#include <stdio.h>
#include <assert.h>//2.0递归版
int In_soda(int num)
{ if(2 >= num)return 1;elsereturn num/2 + In_soda((num/2+num%2));
}
int main()
{printf("%d\n",20+In_soda(20));return 0;
}//1.0普通版
int In_soda(int num)
{int ret = num; while(num>1){ret += num/2;num = num/2 + num%2;}return ret;
}int main()
{printf("%d\n",In_soda(20));return 0;
}

3.模拟实现strcpy

define _CRT_SECURE_NO_WARNINGS 1#include <stdio.h>
#include <assert.h>void my_strcpy(char *dst,const char *src)
{assert(dst);assert(src);while(*dst++ == *src++ && *src != '\0'){;}
}
int main()
{char src[] = "def";char dst[] = "abc";my_strcpy(dst,src);printf("%s",dst);return 0;
}

4.模拟实现strcat

#define _CRT_SECURE_NO_WARNINGS 1#include <stdio.h>
#include <assert.h>void my_strcat(char *dst,const char *src)
{char *tmp = dst;assert(dst);assert(src);while(*tmp != '\0'){tmp++;}while(*src != '\0'){*tmp++ = *src++ ;}*tmp = '\0';
}int main()
{char src[] = "efg";char dst[20] = "abcd";my_strcat(dst,src);printf("%s\n",dst);return 0;
}