1 files changed, 30 insertions, 0 deletions
diff --git a/extension/src/util/lcs.ts b/extension/src/util/lcs.ts
new file mode 100644
index 00000000..17ea63f9
--- /dev/null
+++ b/extension/src/util/lcs.ts
@@ -0,0 +1,30 @@
+export function longestCommonSubsequence(a: string, b: string) {
+  const lengths: number[][] = [];
+  for (let i = 0; i <= a.length; i++) {
+    lengths[i] = [];
+    for (let j = 0; j <= b.length; j++) {
+      if (i === 0 || j === 0) {
+        lengths[i][j] = 0;
+      } else if (a[i - 1] === b[j - 1]) {
+        lengths[i][j] = lengths[i - 1][j - 1] + 1;
+      } else {
+        lengths[i][j] = Math.max(lengths[i - 1][j], lengths[i][j - 1]);
+      }
+    }
+  }
+  let result = "";
+  let x = a.length;
+  let y = b.length;
+  while (x !== 0 && y !== 0) {
+    if (lengths[x][y] === lengths[x - 1][y]) {
+      x--;
+    } else if (lengths[x][y] === lengths[x][y - 1]) {
+      y--;
+    } else {
+      result = a[x - 1] + result;
+      x--;
+      y--;
+    }
+  }
+  return result;
+}