repeating array state after few iterations

Author: Arjiit

prisonAfterNDays.java

@@ -0,0 +1,39 @@
+class Solution {
+/*
+    prison state repeating after a certian number of iterations.
+*/
+    public int[] prisonAfterNDays(int[] cells, int N) {
+        HashSet<String> set = new HashSet<>();
+        int times = 0;
+        boolean flag = false;
+        for (int i=0; i<N; i++) {
+            int[] nextArray = nextDays(cells);
+            String arrString = Arrays.toString(nextArray);
+            if (!set.contains(arrString)) {
+                set.add(arrString);
+                times++;
+            } else {
+                flag = true;
+                break;
+            }
+            cells = nextArray;
+        }
+        if (flag) {
+            N = N%times;
+            for (int i=0; i<N; i++) {
+                cells = nextDays(cells);
+            }
+        }
+        return cells;
+    }
+    
+    public int[] nextDays(int[] cells) {
+        int[] res = new int[cells.length];
+        for(int i=1; i<cells.length -1; i++){
+            if (cells[i-1] == cells[i+1]) {
+               res[i] = 1; 
+            }
+        }
+        return res;
+    }
+}