Update 1643-kth-smallest-instructions.js

Author: everthis

1643-kth-smallest-instructions.js

@@ -49,3 +49,41 @@ function comb(n, r) {
     return product(r + 1, n) / product(1, n - r)
   }
 }
+
+// another
+
+/**
+ * @param {number[]} destination
+ * @param {number} k
+ * @return {string}
+ */
+const kthSmallestPath = function (destination, k) {
+  const [r, c] = destination;
+  const ret = [];
+  let remDown = r;
+  for (let i = 0; i < r + c; i++) {
+    const remSteps = r + c - (i + 1);
+    const com = comb(remSteps, remDown);
+    if (com >= k) ret.push("H");
+    else {
+      remDown -= 1;
+      k -= com;
+      ret.push("V");
+    }
+  }
+  return ret.join("");
+};
+
+function comb(n, r) {
+  if (n < r) return 0;
+  let res = 1;
+  if (n - r < r) r = n - r;
+  for (let i = n, j = 1; i >= 1 && j <= r; --i, ++j) {
+    res = res * i;
+  }
+  for (let i = r; i >= 2; --i) {
+    res = res / i;
+  }
+  return res;
+}
+