Added solution to find the path in given graph

YogenRaii · YogenRaii · commit 49f792ca50ab · 2019-06-27T21:00:47.000-05:00
diff --git a/src/main/java/com/eprogrammerz/examples/algorithm/graphs/ValidPath.java b/src/main/java/com/eprogrammerz/examples/algorithm/graphs/ValidPath.java
@@ -0,0 +1,58 @@
+package com.eprogrammerz.examples.algorithm.graphs;
+
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Queue;
+
+/**
+ * There is a rectangle with left bottom as  (0, 0) and right up as (x, y). There are N circles such that their centers are inside the rectangle.
+ * Radius of each circle is R. Now we need to find out if it is possible that we can move from (0, 0) to (x, y) without touching any circle.
+ * <p>
+ * Note : We can move from any cell to any of its 8 adjecent neighbours and we cannot move outside the boundary of the rectangle at any point of time.
+ */
+public class ValidPath {
+    public String solve(int tx, int ty, int n, int r, List<Integer> cx, List<Integer> cy) {
+        int[] dx = {1, 0, -1, -1, -1, 0, 1, 1};
+        int[] dy = {-1, -1, -1, 0, 1, 1, 1, 0};
+        Queue<int[]> queue = new LinkedList<>();
+        queue.add(new int[]{0, 0});
+
+        boolean[][] visited = new boolean[tx + 1][ty + 1];
+
+        while (!queue.isEmpty()) {
+            int[] cell = queue.poll();
+            int x = cell[0];
+            int y = cell[1];
+            visited[x][y] = true;
+
+            if (x == tx && y == ty) return "YES";
+
+            for (int i = 0; i < 8; i++) {
+                x = x + dx[i];
+                y = y + dy[i];
+
+                if (isValid(x, y, tx, ty, n, r, cx, cy) && !visited[x][y]) {
+                    queue.add(new int[]{x, y});
+                }
+            }
+        }
+        return "NO";
+    }
+
+    private boolean isValid(int x, int y, int tx, int ty, int n, int r, List<Integer> cx, List<Integer> cy) {
+        if (x < 0 || y < 0 || x > tx || y > ty) return false;
+
+        // check if (x,y) falls in one of the circle
+        for (int i = 0; i < n; i++) {
+            int centerX = cx.get(i);
+            int centerY = cy.get(i);
+
+            if (Math.sqrt(Math.pow(x - centerX, 2) + Math.pow(y - centerY, 2)) <= r) {
+                return false;
+            }
+
+        }
+
+        return true;
+    }
+}
