add leetcode: offer-29-31

Author: CodeWater404

Algorithm/src/offer/_29PrintMatrixClockwise.java

@@ -0,0 +1,58 @@
+package offer;
+
+/**
+ * @author ： CodeWater
+ * @create ：2022-07-17-23:43
+ * @Function Description ：29.顺时针打印矩阵
+ */
+public class _29PrintMatrixClockwise {
+    //==========================覆盖原数组的============================
+    class Solution {
+        public int[] spiralOrder(int[][] matrix) {
+            if( matrix.length == 0 ) return new int[0];
+            int n = matrix.length , m = matrix[0].length;
+            int[] res = new int[ n * m ];
+            int x = 0 , y = 0 , d = 0  ;
+            int[] dy = {1 , 0 , -1 , 0} , dx = {0 , 1 , 0 , -1};
+            for( int i = 0 ; i < n * m ; i++ ){
+                res[i] = matrix[x][y];
+                matrix[x][y] = Integer.MAX_VALUE;
+                int a = x + dx[d] , b = y + dy[d];
+                if( a < 0 || a >= n || b < 0 || b >= m || matrix[a][b] == Integer.MAX_VALUE ){
+                    d = (d + 1) % 4;
+                    a = x + dx[d];
+                    b = y + dy[d];
+                }
+                x = a ;
+                y = b;
+            }
+            return res;
+        }
+    }
+    
+    //==========================开一个标志数组的============================
+    class Solution2 {
+        public int[] spiralOrder(int[][] matrix) {
+            if( matrix.length == 0 ) return new int[0];
+            int x = 0 , y = 0 , d = 1;
+            int[] dx = {-1 , 0 , 1 , 0};
+            int[] dy = {0 , 1 , 0 , -1};
+
+            int n = matrix.length ;int m = matrix[0].length;
+            int[] ans = new int[n * m];
+
+            boolean[][] flag = new boolean[n][m];
+            for( int i = 0 ; i < n * m  ; i++ ){
+                flag[x][y] = true;
+                ans[i] = matrix[x][y];
+                int a = x + dx[d]  , b = y + dy[d];
+                if( a < 0 || a >= n || b < 0 || b >= m || flag[a][b] == true ){
+                    d = (d + 1) % 4;
+                    a = x + dx[d] ; b = y + dy[d];
+                }
+                x = a ; y = b;
+            }
+            return ans;
+        }
+    }
+}

Algorithm/src/offer/_31PressingAndPopUpSequencesOfTheStack.java

@@ -0,0 +1,28 @@
+package offer;
+
+import java.util.Stack;
+
+/**
+ * @author ： CodeWater
+ * @create ：2022-07-17-23:52
+ * @Function Description ：31.栈的压入、弹出序列
+ */
+public class _31PressingAndPopUpSequencesOfTheStack {
+    class Solution {
+        // 开一个辅助栈，
+        public boolean validateStackSequences(int[] pushed, int[] popped) {
+            Stack<Integer> stack = new Stack<>();
+            int i = 0;
+            for( int num : pushed ){
+                stack.push(num);
+                // 栈不空，栈顶跟当前弹出顺序值一致就出栈
+                while( !stack.isEmpty() && stack.peek() == popped[i] ){
+                    stack.pop();
+                    i++;
+                }
+            }
+            // 遍历结束，栈中还有元素，那么就不是正确的出栈顺序
+            return stack.isEmpty();
+        }
+    }
+}

Algorithm/src/offer/_57_2AndTheContinuousPositiveNumberSequenceOfSAndS.java

@@ -31,7 +31,7 @@ public int[][] findContinuousSequence(int target) {
     }
 
     //==========================双指针============================
-    class Solution {
+    class Solution2 {
         public int[][] findContinuousSequence(int target) {
             int i = 1 , j =  2 , s = 3;
             List<int[]> res = new ArrayList<>();