Added solution to find the shortest path to remove obstacle

YogenRaii · YogenRaii · commit 0ef32b03421a · 2019-06-09T21:02:04.000-05:00
diff --git a/src/main/java/com/eprogrammerz/examples/algorithm/crackingCoding/ObstacleRemoval.java b/src/main/java/com/eprogrammerz/examples/algorithm/crackingCoding/ObstacleRemoval.java
@@ -0,0 +1,104 @@
+package com.eprogrammerz.examples.algorithm.crackingCoding;
+
+import org.junit.Test;
+
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Queue;
+
+import static org.junit.Assert.assertEquals;
+
+/**
+ * 1 -> valid grid
+ * 0 -> barrier
+ * 9 -> obstacle
+ * Find the shortest path for robot to get to the obstacle starting from top left most grid
+ */
+public class ObstacleRemoval {
+    public int findShortestPath(int rowNum, int colNum, int[][] lot) {
+        boolean[][] visited = new boolean[rowNum][colNum];
+        int[][] distances = new int[rowNum][colNum];
+
+        Queue<Pair> queue = new LinkedList<>();
+        queue.add(new Pair(0,0));
+        distances[0][0] = 0;
+        while (!queue.isEmpty()) {
+            Pair pair = queue.poll();
+            int x = pair.x;
+            int y = pair.y;
+
+            int distance = distances[x][y];
+
+            if (lot[x][y] == 9) return distance;
+
+            visited[x][y] = true;
+
+            if (isValid(x + 1, y, rowNum, colNum, visited, lot)) {
+                queue.add(new Pair(x + 1, y));
+                distances[x + 1][y] = distances[x][y] + 1;
+            }
+
+            if (isValid(x, y + 1, rowNum, colNum, visited, lot)) {
+                queue.add(new Pair(x , y +1));
+                distances[x][y + 1] = distances[x][y] + 1;
+            }
+
+            if (isValid(x - 1, y, rowNum, colNum, visited, lot)) {
+                queue.add(new Pair(x - 1, y));
+                distances[x - 1][y] = distances[x][y] + 1;
+            }
+
+            if (isValid(x, y - 1, rowNum, colNum, visited, lot)) {
+                queue.add(new Pair(x, y - 1));
+                distances[x][y - 1] = distances[x][y] + 1;
+            }
+        }
+        return -1;
+    }
+
+    private boolean isValid(int x, int y, int rowNum, int colNum, boolean[][] visited, int[][] lot) {
+        if (x >= 0 && x < rowNum && y >= 0 && y < colNum && !visited[x][y] && (lot[x][y] == 1 || lot[x][y] == 9)) {
+            return true;
+        }
+        return false;
+    }
+
+    private class Pair {
+        int x;
+        int y;
+        Pair(int x, int y) {
+            this.x = x;
+            this.y = y;
+        }
+
+        @Override
+        public String toString() {
+            return "(" + x + ", " + y + ")";
+        }
+    }
+
+    @Test
+    public void testShortestPath() {
+        int[][] lot1 = new int[][] {
+                {1,0,0},
+                {1,0,0},
+                {1,9,0}
+        };
+        assertEquals(3, findShortestPath(3,3,lot1));
+
+        int[][] lot2 = new int[][] {
+                {1,0,0},
+                {1,1,0},
+                {1,1,9}
+        };
+        assertEquals(4, findShortestPath(3,3,lot2));
+
+        int[][] lot3 = new int[][] {
+                {1,1,1,1},
+                {1,1,0,1},
+                {1,0,0,9},
+                {1,1,1,1}
+        };
+        assertEquals(5, findShortestPath(4,4,lot3));
+    }
+}
