"Edit Distance"

Author: lennylxx

README.md

@@ -19,7 +19,7 @@ them with C++ Language.
 | 63  | [Unique Paths II]                     | [C](src/63.c)      |
 | 64  | [Minimum Path Sum]                    | [C](src/64.c)      |
 | 70  | [Climbing Stairs]                     | [C](src/70.c)      |
-| 72  | [Edit Distance]                       |                    |
+| 72  | [Edit Distance]                       | [C](src/72.c)      |
 | 85  | [Maximal Rectangle]                   |                    |
 | 87  | [Scramble String]                     |                    |
 | 91  | [Decode Ways]                         | [C](src/91.c)      |

src/72.c

@@ -0,0 +1,53 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+int min(int a, int b, int c) {
+    int min = a;
+    if (b < min) min = b;
+    if (c < min) min = c;
+    return min;
+}
+
+int minDistance(char *word1, char *word2) {
+    int len1 = strlen(word1);
+    int len2 = strlen(word2);
+    
+    /* these two lines can be commented out */
+    if (len1 == 0) return len2;
+    if (len2 == 0) return len1;
+    
+    int(*d)[len2 + 1] = (int (*)[len2 + 1])calloc((len1 + 1) * (len2 + 1), sizeof(int));
+    int i, j;
+    
+    d[0][0] = 0; /* dummy */
+    for (i = 1; i <= len1; i++) d[i][0] = i;
+    for (j = 1; j <= len2; j++) d[0][j] = j;
+    
+    for (i = 1; i <= len1; i++){
+        for (j = 1; j <= len2; j++) {
+            /* d[i][j] represents distance of word1[0..i-1] and word2[0..j-1] */
+            if (word1[i - 1] == word2[j - 1]) {
+                d[i][j] = d[i - 1][j - 1];
+            }
+            else {
+                d[i][j] = min(
+                    d[i][j - 1] + 1, /* insert a character(word2[j-1]) to the tail of word1[0..i-1] */
+                    d[i - 1][j] + 1, /* delete a character(word1[i-1]) from the tail of word1[0..i-1] */
+                    d[i - 1][j - 1] + 1 /* replace a character in tail of word1[0..i-1] */
+                    );
+            }
+        }
+    }
+    return d[len1][len2];
+}
+
+int main() {
+    printf("%d %d\n", minDistance("word", "wood"), 1);
+    printf("%d %d\n", minDistance("word", "woord"), 1);
+    printf("%d %d\n", minDistance("d", "word"), 3);
+    printf("%d %d\n", minDistance("", "word"), 4);
+    printf("%d %d\n", minDistance("abcd", "word"), 3);
+    printf("%d %d\n", minDistance("ffff", "word"), 4);
+    return 0;
+}