add zig codes for Section 'Binary Tree' (#292)

* add zig codes for Section 'Binary Tree'

* add zig codes for Section 'Binary Tree'

codes/zig/build.zig

@@ -268,6 +268,19 @@ pub fn build(b: *std.build.Builder) void {
         const run_step_binary_tree= b.step("run_binary_tree", "Run binary_tree");
         run_step_binary_tree.dependOn(&run_cmd_binary_tree.step);
 
+        // Source File: "chapter_tree/binary_tree_bfs.zig"
+        // Run Command: zig build run_binary_tree_bfs
+        const exe_binary_tree_bfs = b.addExecutable("binary_tree_bfs", "chapter_tree/binary_tree_bfs.zig");
+        exe_binary_tree_bfs.addPackagePath("include", "include/include.zig");
+        exe_binary_tree_bfs.setTarget(target);
+        exe_binary_tree_bfs.setBuildMode(mode);
+        exe_binary_tree_bfs.install();
+        const run_cmd_binary_tree_bfs = exe_binary_tree_bfs.run();
+        run_cmd_binary_tree_bfs.step.dependOn(b.getInstallStep());
+        if (b.args) |args| run_cmd_binary_tree_bfs.addArgs(args);
+        const run_step_binary_tree_bfs = b.step("run_binary_tree_bfs", "Run binary_tree_bfs");
+        run_step_binary_tree_bfs.dependOn(&run_cmd_binary_tree_bfs.step);
+        
     // Section: "Heap"
         // Source File: "chapter_heap/heap.zig"
         // Run Command: zig build run_heap

codes/zig/chapter_tree/binary_tree_bfs.zig

@@ -0,0 +1,58 @@
+// File: binary_tree_bfs.zig
+// Created Time: 2023-01-15
+// Author: sjinzh (sjinzh@gmail.com)
+
+const std = @import("std");
+const inc = @import("include");
+
+// 层序遍历
+fn hierOrder(comptime T: type, mem_allocator: std.mem.Allocator, root: *inc.TreeNode(T)) !std.ArrayList(T) {
+    // 初始化队列，加入根结点
+    const L = std.TailQueue(*inc.TreeNode(T));
+    var queue = L{};
+    var root_node = try mem_allocator.create(L.Node);
+    root_node.data = root;
+    queue.append(root_node); 
+    // 初始化一个列表，用于保存遍历序列
+    var list = std.ArrayList(T).init(std.heap.page_allocator);
+    while (queue.len > 0) {
+        var queue_node = queue.popFirst().?;    // 队列出队
+        var node = queue_node.data;
+        try list.append(node.val);              // 保存结点
+        if (node.left != null) {
+            var tmp_node = try mem_allocator.create(L.Node);
+            tmp_node.data = node.left.?;
+            queue.append(tmp_node);             // 左子结点入队
+        }
+        if (node.right != null) {
+            var tmp_node = try mem_allocator.create(L.Node);
+            tmp_node.data = node.right.?;
+            queue.append(tmp_node);             // 右子结点入队
+        }        
+    }
+    return list;
+}
+
+// Driver Code
+pub fn main() !void {
+    // 初始化内存分配器
+    var mem_arena = std.heap.ArenaAllocator.init(std.heap.page_allocator);
+    defer mem_arena.deinit();
+    const mem_allocator = mem_arena.allocator();
+
+    // 初始化二叉树
+    // 这里借助了一个从数组直接生成二叉树的函数
+    var nums = [_]i32{1, 2, 3, 4, 5, 6, 7};
+    var root = try inc.TreeUtil.arrToTree(i32, mem_allocator, &nums);
+    std.debug.print("初始化二叉树\n", .{});
+    try inc.PrintUtil.printTree(root, null, false);
+
+    // 层序遍历
+    var list = try hierOrder(i32, mem_allocator, root.?);
+    defer list.deinit();
+    std.debug.print("\n层序遍历的结点打印序列 = ", .{});
+    inc.PrintUtil.printList(i32, list);
+
+    const getchar = try std.io.getStdIn().reader().readByte();
+    _ = getchar;
+}