Merge pull request wangzheng0822#265 from WayneCui/master

fix levenshtein dist of python version and add JS version

javascript/42_dynamic_programming/levenshtein_distance.js

@@ -0,0 +1,54 @@
+function lsDist(str1, str2) {
+    var n = str1.length;
+    var m = str2.length;
+
+    var memo = new Array(n);
+    for(let i = 0; i < n; i++) {
+        memo[i] = new Array(m);
+        if (str1[i] === str2[0]) {
+            memo[i][0] = i - 0;
+        } else if(i === 0) {
+            memo[i][0] = 1;
+        } else {
+            memo[i][0] = memo[i - 1][0] + 1;
+        }
+    }
+
+    for(let j = 0; j < m; j++) {
+        if(str1[0] === str2[j]) {
+            memo[0][j] = j - 0;
+        } else if(j === 0) {
+            memo[0][j] = 1;
+        } else {
+            memo[0][j] = memo[0][j - 1] + 1;
+        }
+    }
+
+    for(let i = 1; i < n; i++) {
+        for(let j = 1; j < m; j++) {
+            if(str1[i] === str2[j]) {
+                memo[i][j] = Math.min(memo[i - 1][j] + 1, memo[i][j - 1] + 1, memo[i - 1][j - 1 ]);
+            } else {
+                memo[i][j] = Math.min(memo[i - 1][j] + 1, memo[i][j - 1] + 1, memo[i - 1][j - 1 ] + 1);
+            }
+        }
+    }
+    console.log(memo);
+
+    return memo[n - 1][m - 1];
+}
+
+
+var s = "mitcmu";
+var t = "mtacnu";
+
+console.log( lsDist(s, t) );
+
+var s = "kitten";
+var t = "sitting";
+
+console.log( lsDist(s, t) );
+
+var s = "flaw";
+var t = "lawn";
+console.log( lsDist(s, t) );

python/42_dynamic_programming/min_edit_dist.py

@@ -4,13 +4,29 @@
 
 def levenshtein_dp(s: str, t: str) -> int:
     m, n = len(s), len(t)
-    table = [[0] * (n + 1) for _ in range(m + 1)]
-    table[0] = [j for j in range(m + 1)]
-    for i in range(m + 1):
-        table[i][0] = i
-    for i in range(1, m + 1):
-        for j in range(1, n + 1):
-            table[i][j] = min(1 + table[i - 1][j], 1 + table[i][j - 1], int(s[i - 1] != t[j - 1]) + table[i - 1][j - 1])
+    table = [[0] * (n) for _ in range(m)]
+
+    for i in range(n):
+        if s[0] == t[i]:
+            table[0][i] = i - 0
+        elif i != 0:
+            table[0][i] = table[0][i - 1] + 1
+        else:
+            table[0][i] = 1
+
+    for i in range(m):
+        if s[i] == t[0]:
+            table[i][0] = i - 0
+        elif i != 0:
+            table[i][0] = table[i - 1][0] + 1
+        else:
+            table[i][0] = 1
+
+    for i in range(1, m):
+        for j in range(1, n):
+            table[i][j] = min(1 + table[i - 1][j], 1 + table[i][j - 1], int(s[i] != t[j]) + table[i - 1][j - 1])
+
+    print(table)
     return table[-1][-1]
 
 
@@ -27,5 +43,17 @@ def common_substring_dp(s: str, t: str) -> int:
     s = "mitcmu"
     t = "mtacnu"
 
+    print(levenshtein_dp(s, t))
+    print(common_substring_dp(s, t))
+
+    s = "kitten"
+    t = "sitting"
+
+    print(levenshtein_dp(s, t))
+    print(common_substring_dp(s, t))
+
+    s = "flaw"
+    t = "lawn"
+
     print(levenshtein_dp(s, t))
     print(common_substring_dp(s, t))