dp pallindromic subsequence pattern

kaustubhdeokar · Sep 21, 2024 · 69f6146 · 69f6146
1 parent 5d370e6
commit 69f6146
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Showing 4 changed files with 83 additions and 32 deletions.
diff --git a/topics/topics/dp/lcs/LongestCommonSubsequence.java b/topics/topics/dp/lcs/LongestCommonSubsequence.java
@@ -11,45 +11,70 @@ public static void main(String[] args) {
         LongestCommonSubsequence lcs = new LongestCommonSubsequence();
         System.out.println(lcs.recursive(s1, s2));
         System.out.println(lcs.topDown(s1, s2));
+
+        lcs.pallindromicCase();
+
+    }
+
+    private void pallindromicCase() {
+        String s1 = "agbcba";
+        StringBuilder stringBuilder = new StringBuilder();
+        for (int i = s1.length() - 1; i >= 0; i--) {
+            stringBuilder.append(s1.charAt(i));
+        }
+        String s2 = stringBuilder.toString();
+        System.out.println("s1:" + s1);
+        System.out.println("s2:" + s2);
+
+        int matches = topDown(s1, s2);
+        System.out.println(matches);
+
     }
 
     public int recursive(String s1, String s2) {
-        return recursive(s1, s1.length() - 1, s2, s2.length() - 1);
+        return recursive(s1, s1.length(), s2, s2.length());
     }
 
-    public int recursive(String x, int i, String y, int j) {
-        if (i < 0 || j < 0) {
+    private int recursive(String x, int i, String y, int j) {
+        if (i == 0 || j == 0) {
             return 0;
         }
-        if (x.charAt(i) == y.charAt(j)) {
+        if (x.charAt(i - 1) == y.charAt(j - 1)) {
             return 1 + recursive(x, i - 1, y, j - 1);
         } else {
             return Integer.max(recursive(x, i - 1, y, j), recursive(x, i, y, j - 1));
         }
     }
 
-    public int topDown(String x, String y) {
-        int[][] dp = new int[x.length() + 1][y.length() + 1];
+    public int[][] topDownReturnsArr(String x, String y){
+        int xlen = x.length();
+        int ylen = y.length();
+        int[][] dp = new int[xlen + 1][ylen + 1];
         for (int[] arr : dp) {
             Arrays.fill(arr, -1);
         }
+        topDown(dp, x, xlen, y, ylen);
+        return dp;
+    }
 
-        return topDown(dp, x, x.length() - 1, y, y.length() - 1);
+    public int topDown(String x, String y) {
+        int[][] dp = topDownReturnsArr(x, y);
+        return dp[x.length()][y.length()];
     }
 
-    private int topDown(int[][] dp, String x, int i, String y, int j) {
-        if (i < 0 || j < 0) return 0;
+    private int topDown(int[][] dp, String x, int xitr, String y, int yitr) {
+        if (xitr <= 0 || yitr <= 0) return 0;
 
-        if (dp[i][j] != -1) {
-            return dp[i][j];
+        if (dp[xitr][yitr] != -1) {
+            return dp[xitr][yitr];
         }
 
-        if (x.charAt(i) == y.charAt(j)) {
-            dp[i][j] = 1 + topDown(dp, x, i - 1, y, j - 1);
+        if (x.charAt(xitr - 1) == y.charAt(yitr - 1)) {
+            dp[xitr][yitr] = 1 + topDown(dp, x, xitr - 1, y, yitr - 1);
         } else {
-            dp[i][j] = Integer.max(topDown(dp, x, i - 1, y, j), topDown(dp, x, i, y, j - 1));
+            dp[xitr][yitr] = Integer.max(topDown(dp, x, xitr - 1, y, yitr), topDown(dp, x, xitr, y, yitr - 1));
         }
-        return dp[i][j];
+        return dp[xitr][yitr];
     }
 
 }
diff --git a/topics/topics/dp/lcs/LongestPallindromicSubsequence.java b/topics/topics/dp/lcs/LongestPallindromicSubsequence.java
@@ -0,0 +1,26 @@
+package dp.lcs;
+
+import java.util.Collections;
+
+public class LongestPallindromicSubsequence {
+
+    public static void main(String[] args) {
+
+        String s1 = "agbcba";
+
+        StringBuilder stringBuilder = new StringBuilder();
+        for (int i = s1.length() - 1; i >= 0; i--) {
+            stringBuilder.append(s1.charAt(i));
+        }
+        String s2 = stringBuilder.toString();
+        System.out.println("s1:"+s1);
+        System.out.println("s2:"+s2);
+
+    }
+
+    private void lcs(String s1, String s2){
+
+
+    }
+
+}
diff --git a/topics/topics/dp/lcs/MinimumInsertionDeletionToCreateString.java b/topics/topics/dp/lcs/MinimumInsertionDeletionToCreateString.java
@@ -6,7 +6,7 @@ public class MinimumInsertionDeletionToCreateString {
 
     public static void main(String[] args) {
 
-        String from = "abcde";
+        String from = "abcdasdade";
         String to = "acdef";
         MinimumInsertionDeletionToCreateString min = new MinimumInsertionDeletionToCreateString();
         String lcs = min.convertString(from, to);

diff --git a/topics/topics/dp/lcs/PrintLCS.java b/topics/topics/dp/lcs/PrintLCS.java
@@ -2,16 +2,16 @@
 
 public class PrintLCS {
     public static void main(String[] args) {
-        String s1 = "aggtab";
-        String s2 = "gxtxaby";
+        String s1 = "agbcba";
+        String s2 = "abcbga";
         PrintLCS printLCS = new PrintLCS();
         System.out.println(printLCS.topDown(s1, s2));
     }
 
     public String topDown(String x, String y) {
-        int[][] dp = new int[x.length()][y.length()];
-        topDown(dp, x, x.length() - 1, y, y.length() - 1);
-        return calculateLcsString(dp, x, x.length() - 1, y, y.length() - 1);
+        LongestCommonSubsequence lcs = new LongestCommonSubsequence();
+        int[][] dp = lcs.topDownReturnsArr(x, y);
+        return calculateLcsString(dp, x, x.length(), y, y.length());
     }
 
     private String calculateLcsString(int[][] dp, String x, int x1, String y, int y1) {
@@ -24,10 +24,10 @@ private String calculateLcsString(int[][] dp, String x, int x1, String y, int y1
 
         StringBuilder res = new StringBuilder();
 
-        while (x1 >= 0 && y1 >= 0) {
+        while (x1 > 0 && y1 > 0) {
 
-            if (x.charAt(x1) == y.charAt(y1)) {
-                res.append(x.charAt(x1));
+            if (x.charAt(x1-1) == y.charAt(y1-1)) {
+                res.append(x.charAt(x1-1));
                 x1 -= 1;
                 y1 -= 1;
             } else if (dp[x1 - 1][y1] > dp[x1][y1 - 1]) {
@@ -40,19 +40,19 @@ private String calculateLcsString(int[][] dp, String x, int x1, String y, int y1
         return res.toString();
     }
 
-    private int topDown(int[][] dp, String x, int i, String y, int j) {
-        if (i < 0 || j < 0) return 0;
+    private int topDown(int[][] dp, String x, int xitr, String y, int yitr) {
+        if (xitr == 0 || yitr == 0) return 0;
 
-        if (dp[i][j] != 0) {
-            return dp[i][j];
+        if (dp[xitr][yitr] != 0) {
+            return dp[xitr][yitr];
         }
 
-        if (x.charAt(i) == y.charAt(j)) {
-            dp[i][j] = 1 + topDown(dp, x, i - 1, y, j - 1);
+        if (x.charAt(xitr - 1) == y.charAt(yitr - 1)) {
+            dp[xitr][yitr] = 1 + topDown(dp, x, xitr - 1, y, yitr - 1);
         } else {
-            dp[i][j] = Integer.max(topDown(dp, x, i - 1, y, j), topDown(dp, x, i, y, j - 1));
+            dp[xitr][yitr] = Integer.max(topDown(dp, x, xitr - 1, y, yitr), topDown(dp, x, xitr, y, yitr - 1));
         }
-        return dp[i][j];
+        return dp[xitr][yitr];
     }
 
 }