66 lines
1.3 KiB
Java
66 lines
1.3 KiB
Java
// Find maximum palindromic subsequence of the given string
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public class MaxPalindrome {
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public static String maxPalindrome(String p) {
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int n = p.length();
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char[] s = p.toCharArray();
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int[][] dp = new int[n + 1][n + 1];
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for (int i = 0; i <= n; i++) {
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dp[i][0] = dp[0][i] = i;
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}
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for (int i = 0; i < n; i++) {
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for (int j = 0; j < n - 1 - i; j++) {
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dp[i + 1][j + 1] = (s[i] == s[n - 1 - j]) ? dp[i][j] : Math.min(dp[i][j + 1] + 1, dp[i + 1][j] + 1);
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}
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}
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int min = n;
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int x = 0;
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int y = n;
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for (int i = 0; i <= n; i++) {
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if (min > dp[i][n - i]) {
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min = dp[i][n - i];
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x = i;
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y = n - i;
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}
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}
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String middle = "";
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for (int i = 0; i < n; i++) {
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if (min > dp[i][n - i - 1]) {
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min = dp[i][n - i - 1];
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x = i;
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y = n - i - 1;
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middle = "" + s[i];
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}
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}
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String res = "";
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while (x > 0 && y > 0) {
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int a = dp[x - 1][y - 1];
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int b = dp[x - 1][y];
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int c = dp[x][y - 1];
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int m = Math.min(a, Math.min(b, c));
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if (a == m) {
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res += s[x - 1];
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--x;
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--y;
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} else if (b == m) {
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--x;
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} else {
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--y;
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}
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}
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return new StringBuilder(res).reverse() + middle + res;
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}
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// Usage example
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public static void main(String[] args) {
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String res = maxPalindrome("3213");
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System.out.println("323".equals(res));
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}
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}
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