Add _498.Solution2 And Test3 & 4 (#131)

Author: WillShen7789

src/main/java/com/fishercoder/solutions/_498.java

@@ -1,5 +1,9 @@
 package com.fishercoder.solutions;
 
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+
 public class _498 {
 
     public static class Solutoin1 {
@@ -47,4 +51,51 @@ public int[] findDiagonalOrder(int[][] matrix) {
         }
     }
 
+    /*
+        matrix = new int[][]{
+                {1, 2, 3},
+                {4, 5, 6},
+                {7, 8, 9},
+                {10, 11, 12},
+                {13, 14, 15},
+        };
+        expected = new int[]{1, 2, 4, 7, 5, 3, 6, 8, 10, 13, 11, 9, 12, 14, 15};
+    */
+    public static class Solutoin2 {
+        public int[] findDiagonalOrder(int[][] matrix) {
+                if(matrix == null || matrix.length == 0){
+                    return new int[0];
+                }
+                List<List<Integer>> diagonals = new ArrayList<>();
+    			int maxRow = matrix.length;
+    			int maxCol = matrix[0].length;
+    			int maxDiagonal = maxRow + maxCol - 1;
+    			for (int diagonalIndex = 0; diagonalIndex < maxDiagonal; diagonalIndex++) {
+    				int curRowIdx = (diagonalIndex < maxCol) ? 0 : (diagonalIndex - maxCol + 1);
+    				int curColIdx = (diagonalIndex < maxCol) ? diagonalIndex : (maxCol - 1);
+    				List<Integer> diagonal = new ArrayList<Integer>();
+    				while (curRowIdx >= 0 && curRowIdx < maxRow && curColIdx >= 0 && curColIdx < maxCol) {
+    					int diagonalElement = matrix[curRowIdx][curColIdx];
+    					diagonal.add(diagonalElement);
+    					curRowIdx++;
+    					curColIdx--;
+    				}
+    				diagonals.add(diagonal);
+    			}
+    			int[] result = new int[maxRow * maxCol];
+    			int resultIdx = 0;
+    			for (int i = 0; i < diagonals.size(); i++) {
+    				List<Integer> diagonal = diagonals.get(i);
+    				if (i % 2 == 0) {
+    					Collections.reverse(diagonal);
+    				}
+    				for (int j = 0; j < diagonal.size(); j++) {
+    					result[resultIdx] = diagonal.get(j);
+    					resultIdx++;
+    				}
+    			}
+    			return result;
+        }
+    }
+    
 }

src/test/java/com/fishercoder/_498Test.java

@@ -11,12 +11,14 @@
  */
 public class _498Test {
     private static _498.Solutoin1 solutoin1;
+    private static _498.Solutoin2 solutoin2;
     private static int[][] matrix;
     private static int[] expected;
 
     @BeforeClass
     public static void setup() {
         solutoin1 = new _498.Solutoin1();
+        solutoin2 = new _498.Solutoin2();
     }
 
     @Test
@@ -42,4 +44,24 @@ public void test2() {
         expected = new int[]{1, 2, 4, 7, 5, 3, 6, 8, 10, 13, 11, 9, 12, 14, 15};
         assertArrayEquals(expected, solutoin1.findDiagonalOrder(matrix));
     }
+
+    @Test
+    public void test3() {
+        matrix = new int[][]{
+                {1, 2, 3},
+                {4, 5, 6},
+                {7, 8, 9},
+        };
+        expected = new int[]{1, 2, 4, 7, 5, 3, 6, 8, 9};
+        assertArrayEquals(expected, solutoin2.findDiagonalOrder(matrix));
+    }
+    
+    @Test
+    public void test4() {
+        matrix = new int[][]{
+        	{2,5},{8,4},{0,-1}
+        };
+        expected = new int[]{2,5,8,0,4,-1};
+        assertArrayEquals(expected, solutoin2.findDiagonalOrder(matrix));
+    }
 }