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translation: Add Python and Java code for EN version (#1345)
* Add the intial translation of code of all the languages * test * revert * Remove * Add Python and Java code for EN version
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Yudong Jin
139
en/codes/java/chapter_dynamic_programming/edit_distance.java
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139
en/codes/java/chapter_dynamic_programming/edit_distance.java
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/**
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* File: edit_distance.java
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* Created Time: 2023-07-13
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* Author: krahets (krahets@163.com)
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*/
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package chapter_dynamic_programming;
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import java.util.Arrays;
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public class edit_distance {
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/* Edit distance: Brute force search */
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static int editDistanceDFS(String s, String t, int i, int j) {
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// If both s and t are empty, return 0
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if (i == 0 && j == 0)
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return 0;
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// If s is empty, return the length of t
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if (i == 0)
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return j;
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// If t is empty, return the length of s
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if (j == 0)
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return i;
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// If the two characters are equal, skip these two characters
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if (s.charAt(i - 1) == t.charAt(j - 1))
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return editDistanceDFS(s, t, i - 1, j - 1);
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// The minimum number of edits = the minimum number of edits from three operations (insert, remove, replace) + 1
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int insert = editDistanceDFS(s, t, i, j - 1);
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int delete = editDistanceDFS(s, t, i - 1, j);
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int replace = editDistanceDFS(s, t, i - 1, j - 1);
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// Return the minimum number of edits
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return Math.min(Math.min(insert, delete), replace) + 1;
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}
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/* Edit distance: Memoized search */
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static int editDistanceDFSMem(String s, String t, int[][] mem, int i, int j) {
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// If both s and t are empty, return 0
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if (i == 0 && j == 0)
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return 0;
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// If s is empty, return the length of t
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if (i == 0)
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return j;
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// If t is empty, return the length of s
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if (j == 0)
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return i;
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// If there is a record, return it
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if (mem[i][j] != -1)
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return mem[i][j];
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// If the two characters are equal, skip these two characters
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if (s.charAt(i - 1) == t.charAt(j - 1))
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return editDistanceDFSMem(s, t, mem, i - 1, j - 1);
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// The minimum number of edits = the minimum number of edits from three operations (insert, remove, replace) + 1
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int insert = editDistanceDFSMem(s, t, mem, i, j - 1);
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int delete = editDistanceDFSMem(s, t, mem, i - 1, j);
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int replace = editDistanceDFSMem(s, t, mem, i - 1, j - 1);
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// Record and return the minimum number of edits
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mem[i][j] = Math.min(Math.min(insert, delete), replace) + 1;
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return mem[i][j];
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}
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/* Edit distance: Dynamic programming */
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static int editDistanceDP(String s, String t) {
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int n = s.length(), m = t.length();
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int[][] dp = new int[n + 1][m + 1];
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// State transition: first row and first column
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for (int i = 1; i <= n; i++) {
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dp[i][0] = i;
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}
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for (int j = 1; j <= m; j++) {
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dp[0][j] = j;
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}
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// State transition: the rest of the rows and columns
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for (int i = 1; i <= n; i++) {
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for (int j = 1; j <= m; j++) {
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if (s.charAt(i - 1) == t.charAt(j - 1)) {
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// If the two characters are equal, skip these two characters
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dp[i][j] = dp[i - 1][j - 1];
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} else {
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// The minimum number of edits = the minimum number of edits from three operations (insert, remove, replace) + 1
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dp[i][j] = Math.min(Math.min(dp[i][j - 1], dp[i - 1][j]), dp[i - 1][j - 1]) + 1;
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}
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}
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}
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return dp[n][m];
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}
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/* Edit distance: Space-optimized dynamic programming */
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static int editDistanceDPComp(String s, String t) {
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int n = s.length(), m = t.length();
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int[] dp = new int[m + 1];
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// State transition: first row
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for (int j = 1; j <= m; j++) {
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dp[j] = j;
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}
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// State transition: the rest of the rows
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for (int i = 1; i <= n; i++) {
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// State transition: first column
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int leftup = dp[0]; // Temporarily store dp[i-1, j-1]
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dp[0] = i;
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// State transition: the rest of the columns
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for (int j = 1; j <= m; j++) {
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int temp = dp[j];
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if (s.charAt(i - 1) == t.charAt(j - 1)) {
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// If the two characters are equal, skip these two characters
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dp[j] = leftup;
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} else {
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// The minimum number of edits = the minimum number of edits from three operations (insert, remove, replace) + 1
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dp[j] = Math.min(Math.min(dp[j - 1], dp[j]), leftup) + 1;
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}
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leftup = temp; // Update for the next round of dp[i-1, j-1]
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}
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}
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return dp[m];
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}
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public static void main(String[] args) {
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String s = "bag";
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String t = "pack";
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int n = s.length(), m = t.length();
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// Brute force search
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int res = editDistanceDFS(s, t, n, m);
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System.out.println("Changing " + s + " to " + t + " requires a minimum of " + res + " edits");
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// Memoized search
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int[][] mem = new int[n + 1][m + 1];
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for (int[] row : mem)
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Arrays.fill(row, -1);
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res = editDistanceDFSMem(s, t, mem, n, m);
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System.out.println("Changing " + s + " to " + t + " requires a minimum of " + res + " edits");
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// Dynamic programming
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res = editDistanceDP(s, t);
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System.out.println("Changing " + s + " to " + t + " requires a minimum of " + res + " edits");
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// Space-optimized dynamic programming
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res = editDistanceDPComp(s, t);
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System.out.println("Changing " + s + " to " + t + " requires a minimum of " + res + " edits");
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}
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}
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