68 lines
2.2 KiB
Java
68 lines
2.2 KiB
Java
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package DynamicProgramming;
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class LongestCommonSubsequence {
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public static String getLCS(String str1, String str2) {
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//At least one string is null
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if (str1 == null || str2 == null)
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return null;
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//At least one string is empty
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if (str1.length() == 0 || str2.length() == 0)
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return "";
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String[] arr1 = str1.split("");
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String[] arr2 = str2.split("");
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//lcsMatrix[i][j] = LCS of first i elements of arr1 and first j characters of arr2
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int[][] lcsMatrix = new int[arr1.length + 1][arr2.length + 1];
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for (int i = 0; i < arr1.length + 1; i++)
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lcsMatrix[i][0] = 0;
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for (int j = 1; j < arr2.length + 1; j++)
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lcsMatrix[0][j] = 0;
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for (int i = 1; i < arr1.length + 1; i++) {
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for (int j = 1; j < arr2.length + 1; j++) {
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if (arr1[i - 1].equals(arr2[j - 1])) {
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lcsMatrix[i][j] = lcsMatrix[i - 1][j - 1] + 1;
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} else {
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lcsMatrix[i][j] = lcsMatrix[i - 1][j] > lcsMatrix[i][j - 1] ? lcsMatrix[i - 1][j] : lcsMatrix[i][j - 1];
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}
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}
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}
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return lcsString(str1, str2, lcsMatrix);
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}
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public static String lcsString(String str1, String str2, int[][] lcsMatrix) {
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StringBuilder lcs = new StringBuilder();
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int i = str1.length(),
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j = str2.length();
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while (i > 0 && j > 0) {
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if (str1.charAt(i - 1) == str2.charAt(j - 1)) {
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lcs.append(str1.charAt(i - 1));
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i--;
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j--;
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} else if (lcsMatrix[i - 1][j] > lcsMatrix[i][j - 1]) {
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i--;
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} else {
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j--;
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}
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}
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return lcs.reverse().toString();
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}
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public static void main(String[] args) {
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String str1 = "DSGSHSRGSRHTRD";
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String str2 = "DATRGAGTSHS";
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String lcs = getLCS(str1, str2);
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//Print LCS
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if (lcs != null) {
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System.out.println("String 1: " + str1);
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System.out.println("String 2: " + str2);
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System.out.println("LCS: " + lcs);
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System.out.println("LCS length: " + lcs.length());
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}
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}
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}
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