add oct

data/3.C语言高阶/3.位运算/1.位和字节/check.md

@@ -23,7 +23,7 @@ int main(char** args){
 
 ```c
 
-int check(int x) {
+unsigned int check(unsigned int x) {
     if(x < 2){
         return 0;
     }
@@ -48,7 +48,7 @@ int check(int x) {
 
 ```c
 
-int check(int x) {
+unsigned int check(unsigned int x) {
     return x & (x-1) == 0;
 }
 
@@ -57,7 +57,7 @@ int check(int x) {
 ### 边界条件处理的不对
 
 ```c
-int check(int x) {
+unsigned int check(unsigned int x) {
     for(int value = x; value > 0; value = value/2) {
         if((value % 2) != 0){
             return 0;

data/3.C语言高阶/3.位运算/2.二进制数/config.json

@@ -6,5 +6,5 @@
     "C语言"
   ],
   "children": [],
-  "export": []
+  "export": ["count.json"]
 }
\ No newline at end of file

data/3.C语言高阶/3.位运算/2.二进制数/count.json

+{
+    "type": "code_options",
+    "author": "刘鑫",
+    "source": "check.md",
+    "exercise_id":"277ffa9a36b648c8a55a512c7e5daf99"
+}
\ No newline at end of file

data/3.C语言高阶/3.位运算/2.二进制数/cout.md

+# 计算位数
+
+计算整数的二进制形式有多少位。
+
+## template
+
+```c
+#include <stdio.h>
+
+$code
+
+int main(char** args){
+    printf("bits(%d) has %d bits\n", 100, bits(100));
+    printf("bits(%d) has %d bits\n", 32, bits(32));
+    printf("bits(%d) has %d bits\n", 10, bits(10));
+    printf("bits(%d) has %d bits\n", 25, bits(25));
+    printf("bits(%d) has %d bits\n", 7, bits(7));
+    return 0;
+}
+```
+
+## 答案
+
+```c
+unsigned int bits(unsigned int x){
+    unsigned int n = 0;
+    while(x){
+        x >>= 1;
+        n++;
+    }
+    return n;
+}
+```
+
+## 选项
+
+### 位移计算没有保存
+
+```c
+unsigned int bits(unsigned int x){
+    unsigned int n = 0;
+    while(x){
+        x >> 1;
+        n++;
+    }
+    return n;
+}
+```
+
+### 没有括号导致流程错误
+
+```c
+unsigned int bits(unsigned int x){
+    unsigned int n = 0;
+    while(x)
+        x >>= 1;
+        n++;
+
+    return n;
+}
+```
+
+### 运算符错误
+
+```c
+unsigned int bits(unsigned int x){
+    unsigned int n = 0;
+    while(x){
+        x << 1;
+        n++;
+    }
+    return n;
+}
+```
\ No newline at end of file

data/3.C语言高阶/3.位运算/3.八进制/config.json

@@ -6,5 +6,5 @@
     "C语言"
   ],
   "children": [],
-  "export": []
+  "export": ["oct.json"]
 }
\ No newline at end of file

data/3.C语言高阶/3.位运算/3.八进制/oct.json

+{
+    "type": "code_options",
+    "author": "刘鑫",
+    "source": "oct.md",
+    "exercise_id":"b15add5a05e84ecdbdf862dcfa722b30"
+}
\ No newline at end of file

data/3.C语言高阶/3.位运算/3.八进制/oct.md

+# 八进制转换
+
+将正整数输出为八进制形式的字符串。现已有申请内存的`create_buffer`函数和释放内存的`free_buffer`
+函数，正确的字符串转换函数是：
+
+## template
+
+```c
+#include <stdio.h>
+#include <stdlib.h>
+
+unsigned int count(unsigned int x) {
+    unsigned int n = 0;
+    while(x){
+        x >>= 3;
+        n++;
+    }
+    return n;
+}
+
+int create_buffer(unsigned int x, char** ref){
+    unsigned int length = count(x);
+    *ref = malloc(length*sizeof(char));
+    return length;
+}
+
+$code
+
+void free_buffer(char** buffer) {
+    free(*buffer);
+}
+
+void print_oct(unsigned int x){
+    char* oct_string = NULL;
+    int len = create_buffer(x, &oct_string);
+    put_oct(x, oct_string, len);
+    printf("%d oct: %s \n", x, oct_string);
+    free_buffer(&oct_string);
+}
+
+int main(char** args){
+    print_oct(100);
+    print_oct(25);
+    print_oct(64);
+    print_oct(15);
+    return 0;
+}
+```
+
+## 答案
+
+```c
+void put_oct(unsigned int x, char* buffer, int n) {
+    char start = '0';
+    while(x){
+        n--;
+        buffer[n] = start + x % 8;
+        x >>= 3;
+    }
+}
+```
+
+## 选项
+
+### 索引错误，会导致内存写越界
+
+```c
+void put_oct(unsigned int x, char* buffer, int n) {
+    char start = '0';
+    while(x){
+        buffer[n] = start + x % 8;
+        n--;
+        x >>= 3;
+    }
+}
+```
+
+### 没写括号导致流程错误
+
+```c
+void put_oct(unsigned int x, char* buffer, int n) {
+    char start = '0';
+    while(x)
+        buffer[--n] = start + x % 8;
+        x >>= 3;
+}
+```
+
+### 位移操作错误
+
+```c
+void put_oct(unsigned int x, char* buffer, int n) {
+    char start = '0';
+    while(x){
+        n--;
+        buffer[n] = start + x % 8;
+        x >>= 8;
+    }
+}
+```
\ No newline at end of file