char[4]转int或int转char

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默认int占4个字节
 
char c1 = 'a';
char c2 = 'b';
char c3 = 'c';
char c4 = 'd';
int i = (c4) + (c3 << 8) + (c2 << 16) + (c3 << 24);
 
数组形式:
char c[5] = "abcd";
int i = 0;
memcpy(&i, c, 4);

1）用库函数itoa

int a = 123;
char str[100];
itoa(a, str, 10);

单个数字转

int ver = 123;
char buf[4] = { 0 };
 
buf[0] = ((ver / 100) % 10) + '0';
buf[1] = ((ver / 10) % 10) + '0';
buf[2] = ((ver) % 10) + '0';
buf[3] = '';