Merge pull request #57 from shivam7147/main

LCS Visualizer

Author: adityacosmos24

package-lock.json

@@ -31,6 +31,7 @@
     "tailwind-merge": "^3.3.1"
   },
   "devDependencies": {
+    "@commitlint/config-conventional": "^20.0.0",
     "@eslint/js": "^9.36.0",
     "@types/node": "^24.7.1",
     "@types/react": "^19.1.16",

package.json

@@ -0,0 +1,57 @@
+export function longestCommonSubsequenceSteps(a = "", b = "") {
+  const m = a.length;
+  const n = b.length;
+
+  // ✅ initialize DP table
+  const dp = Array.from({ length: m + 1 }, () => Array(n + 1).fill(0));
+  const steps = [];
+
+  const snapshot = () => dp.map(row => [...row]);
+
+  // ✅ filling dp table
+  for (let i = 1; i <= m; i++) {
+    for (let j = 1; j <= n; j++) {
+      if (a[i - 1] === b[j - 1]) {
+        dp[i][j] = dp[i - 1][j - 1] + 1;
+        steps.push({
+          dp: snapshot(),
+          active: { i, j },
+          match: { i, j },
+          message: `Characters match '${a[i - 1]}' at A[${i - 1}] & B[${j - 1}] → dp[${i}][${j}] = dp[${i - 1}][${j - 1}] + 1 = ${dp[i][j]}`
+        });
+      } else {
+        dp[i][j] = Math.max(dp[i - 1][j], dp[i][j - 1]);
+        steps.push({
+          dp: snapshot(),
+          active: { i, j },
+          message: `No match. dp[${i}][${j}] = max(dp[${i - 1}][${j}] = ${dp[i - 1][j]}, dp[${i}][${j - 1}] = ${dp[i][j - 1]}) = ${dp[i][j]}`
+        });
+      }
+    }
+  }
+
+  // ✅ traceback to get sequence
+  let i = m, j = n;
+  let lcsChars = [];
+  const path = [];
+
+  while (i > 0 && j > 0) {
+    if (a[i - 1] === b[j - 1]) {
+      lcsChars.push(a[i - 1]);
+      path.push({ i, j });
+      i--;
+      j--;
+    } else if (dp[i - 1][j] >= dp[i][j - 1]) i--;
+    else j--;
+  }
+
+  const finalPath = path.reverse();
+  steps.push({
+    dp: snapshot(),
+    finalPath,
+    message: `Final LCS sequence = '${lcsChars.reverse().join('')}'`,
+    sequence: lcsChars.join('')
+  });
+
+  return steps;
+}