Update the book based on the revised second edition (#1014)

* Revised the book

* Update the book with the second revised edition

* Revise base on the manuscript of the first edition

codes/rust/chapter_backtracking/n_queens.rs

@@ -18,10 +18,10 @@ fn backtrack(row: usize, n: usize, state: &mut Vec<Vec<String>>, res: &mut Vec<V
     }
     // 遍历所有列
     for col in 0..n {
-        // 计算该格子对应的主对角线和副对角线
+        // 计算该格子对应的主对角线和次对角线
         let diag1 = row + n - 1 - col;
         let diag2 = row + col;
-        // 剪枝：不允许该格子所在列、主对角线、副对角线上存在皇后
+        // 剪枝：不允许该格子所在列、主对角线、次对角线上存在皇后
         if !cols[col] && !diags1[diag1] && !diags2[diag2] {
             // 尝试：将皇后放置在该格子
             state.get_mut(row).unwrap()[col] = "Q".into();
@@ -48,7 +48,7 @@ fn n_queens(n: usize) -> Vec<Vec<Vec<String>>> {
     }
     let mut cols = vec![false; n]; // 记录列是否有皇后
     let mut diags1 = vec![false; 2 * n - 1]; // 记录主对角线上是否有皇后
-    let mut diags2 = vec![false; 2 * n - 1]; // 记录副对角线上是否有皇后
+    let mut diags2 = vec![false; 2 * n - 1]; // 记录次对角线上是否有皇后
     let mut res: Vec<Vec<Vec<String>>> = Vec::new();
 
     backtrack(0, n, &mut state, &mut res, &mut cols, &mut diags1, &mut diags2);