Algorithms/src/dynamic_programming/LongestCommonSubsequence.java at main · Flopsey/Algorithms · GitHub

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packagedynamic_programming;

importdata_structures.LinkedList;

publicclassLongestCommonSubsequence {

publicstaticvoidmain(String[] args) {
// Example:
System.out.println(longestCommonSubsequence("ZIEGE".toCharArray(), "TIGER".toCharArray())); // ['I', 'G', 'E']
System.out.println(longestCommonSubsequence("COVID".toCharArray(), "PARTY".toCharArray())); // []
 }

publicstaticLinkedList<Character> longestCommonSubsequence(char[] a, char[] b) {
int[][] table = newint[a.length + 1][b.length + 1];
for (inti = 0; i < a.length + 1; ++i) {
table[i][0] = 0;
 }
for (intj = 0; j < b.length + 1; ++j) {
table[0][j] = 0;
 }

for (inti = 1; i < table.length; ++i) {
for (intj = 1; j < table[i].length; ++j) {
table[i][j] = max(
table[i - 1][j],
table[i][j - 1],
table[i - 1][j - 1] + (a[i - 1] == b[j - 1] ? 1 : 0)
 );
 }
 }

LinkedList<Character> solution = newLinkedList<>();
inti = a.length;
intj = b.length;
while (!(i == 0 || j == 0)) {
charcharA = a[i - 1];
charcharB = b[j - 1];
if (charA == charB) {
solution.addFirst(charA);
i -= 1;
j -= 1;
 } elseif (table[i][j] == table[i][j - 1]) {
j -= 1;
 } else {
i -= 1;
 }
 }
returnsolution;
 }

privatestaticintmax(int... values) {
if (values.length == 0) {
thrownewIllegalArgumentException();
 }
intmax = values[0];
for (inti = 1; i < values.length; ++i) {
max = Math.max(max, values[i]);
 }
returnmax;
 }

}