date:10.4（Content：Mr.Peng）（ C language practice）

void reverse(char* p, int len)
{char* left = p;char* right = p + len - 2;while (left < right){char* temp = left;*left = *right;//当*left=*right后，*temp已经被改为f了*right = *temp;//你再*temp赋值给*right时，已经没用了left++;right--;}}int main()
{char arr[] = "abcdef";int len = sizeof(arr) / sizeof(char);printf("%d\n", len);reverse(arr, len);printf("%s\n", arr);return 0;
}

局部变量是存放在栈上的，栈又是从高到底存放所以先存i后存arr[]

	i
	arr[9]
	arr[8]
	arr[7]
	arr[6]
	arr[5]
	arr[4]
	arr[3]
	arr[2]
	arr[1]
	arr[0]

打印菱形

#include<stdio.h>int main()
{int line = 0;scanf("%d", &line);//7for (int i = 1; i <= line; i++){for (int j = 0; j < line-i; j++){printf(" ");}for (int j = 0; j < 2 * i - 1; j++){printf("*");}printf("\n");}for (int i = 1; i < line; i++){for (int j = 0; j < i; j++){printf(" ");}for (int j = 0; j < 2 * (line - i) - 1; j++){printf("*");}printf("\n");}return 0;
}

凶手是谁？

char killer = 0;
for (killer = 'A'; killer <= 'D'; killer++)
{if ((killer != 'A') + (killer == 'C') + (killer == 'D') + (killer != 'D') == 3){printf("%c\n", killer);}
}