int k = 0, i = 0, j = 0; for (k = 0; k < 30&&i<strlen(str1);){ str[k++] = str1[i++]; } str[k] = '+'; str[++k] = 0; strcat(str, str2); sscanf(str, "%d+%d", &a, &b); printf("%d\n", a + b); } 以上程序实现了str1和str2的字符串相加减,为什么在...