basics

Author: idf

src/EditDistance/Solution.java

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+package EditDistance;
+
+/**
+ * User: Danyang
+ * Date: 1/26/2015
+ * Time: 11:09
+ *
+ * Given two words word1 and word2, find the minimum number of steps required to convert word1 to word2. (each operation
+ * is counted as 1 step.)
+
+ You have the following 3 operations permitted on a word:
+
+ a) Insert a character
+ b) Delete a character
+ c) Replace a character
+ */
+public class Solution {
+    /**
+     * from word1 to word2
+     * f[i, j] the min distance from word1[0..i] tp word2[0..j]
+     * if word1[i]==word2[j]:
+     * f[i][j] = f[i-1][j-1]
+     *
+     * else:
+     * delete: f[i, j] = f[i-1, j]+1
+     * insert: f[i, j] = f[i, j-1]+1
+     * replace f[i, j] = f[i-1, j-1]+1
+     *
+     * Notice:
+     * 1. the INITIAL condition
+     *
+     * @param word1
+     * @param word2
+     * @return
+     */
+    public int minDistance(String word1, String word2) {
+        int m = word1.length();
+        int n = word2.length();
+        int[][] f = new int[m+1][n+1];
+        for(int j=0; j<n+1; j++)
+            f[0][j] = j;
+        for(int i=0; i<m+1; i++)
+            f[i][0] = i;
+
+        for(int i=1; i<m+1; i++)
+            for(int j=1; j<n+1; j++) {
+                if(word1.charAt(i-1)==word2.charAt(j-1))
+                    f[i][j] = f[i-1][j-1];
+                else {
+                    f[i][j] = Math.min(f[i-1][j]+1, Math.min(f[i][j-1]+1, f[i-1][j-1]+1));
+                }
+            }
+        return f[m][n];
+    }
+}

src/RemoveElement/Solution.java

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+package RemoveElement;
+
+/**
+ * User: Danyang
+ * Date: 1/26/2015
+ * Time: 10:58
+ *
+ * Given an array and a value, remove all instances of that value in place and return the new length.
+
+ The order of elements can be changed. It doesn't matter what you leave beyond the new length.
+ */
+public class Solution {
+    /**
+     * Put it to back
+     * @param A
+     * @param elem
+     * @return
+     */
+    public int removeElement(int[] A, int elem) {
+        int e = A.length-1;
+        for(int i=0; i<=e; ) {
+            if(A[i]!=elem)
+                i++;
+            else {
+                int t = A[i]; A[i] = A[e]; A[e] = t;
+                e--;
+            }
+        }
+        return e+1;
+    }
+}