added old projects

CS101/lab_17/.vscode/settings.json

@@ -0,0 +1,4 @@
+{
+    "java.project.sourcePaths": ["src"],
+    "java.project.outputPath": "bin"
+}

CS101/lab_17/README.md

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+## Getting Started
+
+Welcome to the VS Code Java world. Here is a guideline to help you get started to write Java code in Visual Studio Code.
+
+## Folder Structure
+
+The workspace contains two folders by default, where:
+
+- `src`: the folder to maintain sources
+- `lib`: the folder to maintain dependencies
+
+Meanwhile, the compiled output files will be generated in the `bin` folder by default.
+
+> If you want to customize the folder structure, open `.vscode/settings.json` and update the related settings there.
+
+## Dependency Management
+
+The `JAVA PROJECTS` view allows you to manage your dependencies. More details can be found [here](https://github.com/microsoft/vscode-java-dependency#manage-dependencies).

CS101/lab_17/src/App.java

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+public class App {
+    public static void main(String[] args) throws Exception {
+        int arr[][] = {{1, 5, 9,}, 
+                       {8, 3, 4 },
+                       {6, 7, 2 }};
+        Magic matrix = new Magic(arr);
+        System.out.println(matrix.magic());
+    }
+}

CS101/lab_17/src/Magic.java

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+public class Magic {
+    int _matrix[][] = { {1, 5, 9 }, 
+                        {8, 3, 4 },
+                        {6, 7, 2 }};;
+
+    public Magic(int matrix[][]) {
+        if(matrix.length != matrix[0].length) {
+            throw new IllegalArgumentException("Not Square");
+        } else {
+            for (int i = 0; i < matrix.length; i++) {
+                for (int j = 0; j < matrix[0].length; j++) {
+                    _matrix[i][j] = matrix[i][j];
+                }
+            }
+        }
+    }
+
+    public boolean rowSemiMagic() {
+        int rowSums[] = new int[_matrix.length];
+        int sumRow;
+        for (int i = 0; i < _matrix.length; i++) {
+            sumRow = 0;
+            for (int j = 0; j <_matrix[0].length; j++) {
+                sumRow += _matrix[i][j];
+                rowSums[i] = sumRow;
+            }
+        }
+        for (int i = 0; i < rowSums.length; i++) {
+            if (rowSums[0] != rowSums[i]) {
+                return false;
+            }
+        }
+        return true;
+    }
+
+    public boolean columnSemiMagic() {
+        int columnSums[] = new int[_matrix[0].length];
+        int sumColumn;
+        for (int i = 0; i < _matrix.length; i++) {
+            sumColumn = 0;
+            for (int j = 0; j <_matrix[0].length; j++) {
+                sumColumn += _matrix[i][j];
+                columnSums[i] = sumColumn;
+            }
+        }
+        for (int i = 0; i < columnSums.length; i++) {
+            if (columnSums[0] != columnSums[i]) {
+                return false;
+            }
+        }
+        return true;
+    }
+
+    public boolean magic() {
+        if (rowSemiMagic() && columnSemiMagic()) {
+            return true;
+        } else  {
+            return false;
+        }
+    }
+}