build

chapter_computational_complexity/iteration_and_recursion.md

@@ -158,7 +158,15 @@ status: new
 === "C"
 
     ```c title="iteration.c"
-    [class]{}-[func]{forLoop}
+    /* for 循环 */
+    int forLoop(int n) {
+        int res = 0;
+        // 循环求和 1, 2, ..., n-1, n
+        for (int i = 1; i <= n; ++i) {
+            res += i;
+        }
+        return res;
+    }
     ```
 
 === "Zig"
@@ -344,7 +352,17 @@ status: new
 === "C"
 
     ```c title="iteration.c"
-    [class]{}-[func]{whileLoop}
+    /* while 循环 */
+    int whileLoop(int n) {
+        int res = 0;
+        int i = 1; // 初始化条件变量
+        // 循环求和 1, 2, ..., n-1, n
+        while (i <= n) {
+            res += i;
+            i++; // 更新条件变量
+        }
+        return res;
+    }
     ```
 
 === "Zig"
@@ -539,7 +557,19 @@ status: new
 === "C"
 
     ```c title="iteration.c"
-    [class]{}-[func]{whileLoopII}
+    /* while 循环（两次更新） */
+    int whileLoopII(int n) {
+        int res = 0;
+        int i = 1; // 初始化条件变量
+        // 循环求和 1, 4, ...
+        while (i <= n) {
+            res += i;
+            // 更新条件变量
+            i++;
+            i *= 2;
+        }
+        return res;
+    }
     ```
 
 === "Zig"
@@ -724,7 +754,23 @@ status: new
 === "C"
 
     ```c title="iteration.c"
-    [class]{}-[func]{nestedForLoop}
+    /* 双层 for 循环 */
+    char *nestedForLoop(int n) {
+        // n * n 为对应点数量，"(i, j), " 对应字符串长最大为 6+10*2，加上最后一个空字符 \0 的额外空间
+        int size = n * n * 26 + 1;
+        char *res = malloc(size * sizeof(char));
+
+        // 循环 i = 1, 2, ..., n-1, n
+        for (int i = 1; i <= n; ++i) {
+            // 循环 j = 1, 2, ..., n-1, n
+            for (int j = 1; j <= n; ++j) {
+                char tmp[26];
+                snprintf(tmp, sizeof(tmp), "(%d, %d), ", i, j);
+                strncat(res, tmp, size - strlen(res) - 1);
+            }
+        }
+        return res;
+    }
     ```
 
 === "Zig"
@@ -910,7 +956,16 @@ status: new
 === "C"
 
     ```c title="recursion.c"
-    [class]{}-[func]{recur}
+    /* 递归 */
+    int recur(int n) {
+        // 终止条件
+        if (n == 1)
+            return 1;
+        // 递：递归调用
+        int res = recur(n - 1);
+        // 归：返回结果
+        return n + res;
+    }
     ```
 
 === "Zig"
@@ -1091,7 +1146,14 @@ status: new
 === "C"
 
     ```c title="recursion.c"
-    [class]{}-[func]{tailRecur}
+    /* 尾递归 */
+    int tailRecur(int n, int res) {
+        // 终止条件
+        if (n == 0)
+            return res;
+        // 尾递归调用
+        return tailRecur(n - 1, res + n);
+    }
     ```
 
 === "Zig"
@@ -1278,7 +1340,16 @@ status: new
 === "C"
 
     ```c title="recursion.c"
-    [class]{}-[func]{fib}
+    /* 斐波那契数列：递归 */
+    int fib(int n) {
+        // 终止条件 f(1) = 0, f(2) = 1
+        if (n == 1 || n == 2)
+            return n - 1;
+        // 递归调用 f(n) = f(n-1) + f(n-2)
+        int res = fib(n - 1) + fib(n - 2);
+        // 返回结果 f(n)
+        return res;
+    }
     ```
 
 === "Zig"