练习—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>

void find(int arr[], int sz, int *x, int *y)
{
	int i = 0;
	int j = 0;
	for(i=0; i<sz; i++)
	{
		for(j=0; j<sz; j++)
		{
			if((arr[i] == arr[j]) && (i != j))
				break;
		}
		if(j == sz)
		{
			*x = *y;
			*y = arr[i];
		}
	}
}

int main()
{
	int arr[] = {2,8,3,5,4,7,2,5,4,8};
	int sz = sizeof(arr)/sizeof(arr[0]);
	int x = 0;
	int y = 0;
	int i = 0;
	find(arr, sz, &x, &y);
	for(i=0; i<sz; i++)
	{
		printf("%d ",arr[i]);
	}
	printf("\n");
	printf("只出现一次的是%d和%d\n",x,y);

	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。

#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>

int num_soda(int n)
{
	int sum = n;
	int y = 0;
	while(n)
	{
		if(n % 2 == 1)
		{
			y += 1;
		}
		sum += (n /= 2);
	}
	return sum+(y/2);
}

int main()
{
	int n = 15;
	printf("给%d元，可以喝%d瓶汽水\n",n,num_soda(n));
	return 0;
}

3.模拟实现strcpy

#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
#include<assert.h>

char* my_strcpy(char *dest, const char *src)
{
	char *ret = dest;
	assert(dest != NULL);
	assert(src != NULL);

	while(*dest++ = *src++)
	{
		;
	}
	return ret;
}

int main()
{
	char arr1[] = "abcdefg";
	char arr2[10] = {0};
	my_strcpy(arr2, arr1);
	printf("%s\n",my_strcpy(arr2, arr1));

	return 0;
}

4.模拟实现strcat

#define _CRT_SECURE_NO_WARNINGS 1
#include <stdio.h>
#include<assert.h>
#include <string.h>

char *my_strcat(char *dest, const char *src)
{
	char *ret = dest;
	assert(dest != NULL);
	assert(src != NULL);

	while(*dest)
	{
		dest++;
	}
	while(*src)
	{
		*dest = *src;
		src++;
		dest++;
	}

	return ret;
}

int main()
{
	char a[30] = "tomorrow";
	//附加字符串 char *strcat( char *strDestination, const char *strSource );
	strcat(a," will be");
	my_strcat(a," better!");
	printf("%s\n",a);
	return 0;
}