leetcode — palindrome-partitioning-ii

import java.util.Arrays;

/**
 *
 * Source : https://oj.leetcode.com/problems/palindrome-partitioning-ii/
 *
 * Given a string s, partition s such that every substring of the partition is a palindrome.
 *
 * Return the minimum cuts needed for a palindrome partitioning of s.
 *
 * For example, given s = "aab",
 * Return 1 since the palindrome partitioning ["aa","b"] could be produced using 1 cut.
 */
public class PalindromePartition2 {


    /**
     * 将字符串分割为多个回文字符串的最小分割次数
     *
     * 定义数组cut[len+1]，cut[i]表示从0-的最小分割数，初始化cut[0] = -1,
     * 当i-j是回文字符串的时候，cut[i] = min(cut[i], cut[j]+1)
     *
     * 最后得出的cut[len+1]就是0-(len+1)之间的最小分割数
     *
     * @param str
     * @return
     */
    public int minPartition (String str) {
        if (str.length() <= 1) {
            return 0;
        }
        int[] cut = new int[str.length()+1] ;
        Arrays.fill(cut, Integer.MAX_VALUE);
        boolean[][] table = new boolean[str.length()][str.length()];
        cut[0] = -1;
        for (int i = str.length()-1; i >= 0; i--) {
            for (int j = i; j < str.length(); j++) {
                if ((i+1 > j - 1 || table[i+1][j-1]) && str.charAt(i) == str.charAt(j)) {
                    table[i][j] = true;
                }
            }
        }

        for (int i = 1; i <= str.length(); i++) {
            for (int j = i-1; j > -1; j--) {
                if (table[j][i-1]) {
                    cut[i] = Math.min(cut[i], cut[j] + 1);
                }
            }
        }

        return cut[str.length()];
    }

    public static void main(String[] args) {
        PalindromePartition2 palindromePartition2 = new PalindromePartition2();
        System.out.println(palindromePartition2.minPartition("aab") + "==1");
    }

}