From 1b5c0082efb2224be80f3b8128a1c17a1f1bac99 Mon Sep 17 00:00:00 2001
From: Hans <hans@hansl.ca>
Date: Tue, 4 Sep 2018 14:18:14 -0700
Subject: [PATCH] feat(@angular-devkit/core): add levenshtein distance utility
---
.../angular_devkit/core/src/utils/strings.ts | 49 +++++++++++++++++++
1 file changed, 49 insertions(+)
diff --git a/packages/angular_devkit/core/src/utils/strings.ts b/packages/angular_devkit/core/src/utils/strings.ts
index 4743e9cb65..ff3c0ce7ce 100644
--- a/packages/angular_devkit/core/src/utils/strings.ts
+++ b/packages/angular_devkit/core/src/utils/strings.ts
@@ -127,3 +127,52 @@ export function underscore(str: string): string {
export function capitalize(str: string): string {
return str.charAt(0).toUpperCase() + str.substr(1);
}
+
+/**
+ * Calculate the levenshtein distance of two strings.
+ * See https://en.wikipedia.org/wiki/Levenshtein_distance.
+ * Based off https://gist.github.com/andrei-m/982927 (for using the faster dynamic programming
+ * version).
+ *
+ * @param a String a.
+ * @param b String b.
+ * @returns A number that represents the distance between the two strings. The greater the number
+ * the more distant the strings are from each others.
+ */
+export function levenshtein(a: string, b: string): number {
+ if (a.length == 0) {
+ return b.length;
+ }
+ if (b.length == 0) {
+ return a.length;
+ }
+
+ const matrix = [];
+
+ // increment along the first column of each row
+ for (let i = 0; i <= b.length; i++) {
+ matrix[i] = [i];
+ }
+
+ // increment each column in the first row
+ for (let j = 0; j <= a.length; j++) {
+ matrix[0][j] = j;
+ }
+
+ // Fill in the rest of the matrix
+ for (let i = 1; i <= b.length; i++) {
+ for (let j = 1; j <= a.length; j++) {
+ if (b.charAt(i - 1) == a.charAt(j - 1)) {
+ matrix[i][j] = matrix[i - 1][j - 1];
+ } else {
+ matrix[i][j] = Math.min(
+ matrix[i - 1][j - 1] + 1, // substitution
+ matrix[i][j - 1] + 1, // insertion
+ matrix[i - 1][j] + 1, // deletion
+ );
+ }
+ }
+ }
+
+ return matrix[b.length][a.length];
+}