回文分割
在此算法中,输入是一个字符串,字符串的分割是回文分割,当分割的每个子字符串都是一个回文时。
在此算法中,我们必须找到将给定字符串回文分割所需的最小切分。
输入与输出
Input: A string. Say “ababbbabbababa” Output: Minimum cut to partition as palindrome. Here 3 cuts are needed. The palindromes are: a | babbbab | b | ababa
算法
minPalPart(str)
输入:给定的字符串。
输出:字符串中回文分割的最小数。
Begin n := length of str define cut matrix and pal matrix each of order n x n for i := 0 to n, do pal[i, i] := true cut[i, i] := 0 done for len in range 2 to n, do for i in range 0 to n – len, do j := i + len – 1 if len = 2, then if str[i] = str[j] pal[i, j] := true else if str[i] = str[j] and pal[i+1, j-1] ≠ 0 pal[i, j] := true if pal[i, j] is true, then cut[i, j] := 0 else cut[i, j] := ∞ for k in range i to j-1, do cut[i, j] := minimum of cut[i, j] and (cut[i, k]+ cut[k+1, j+1]+1) done done done return cut[0, n-1] End
示例
#include <iostream> using namespace std; int min (int a, int b) { return (a < b)? a : b; } int minPalPartion(string str) { int n = str.size(); int cut[n][n]; bool pal[n][n]; //true when palindrome present for i to jth element for (int i=0; i<n; i++) { pal[i][i] = true; //substring of length 1 is plaindrome cut[i][i] = 0; } for (int len=2; len<=n; len++) { for (int i=0; i<n-len+1; i++) { //find all substrings of length len int j = i+len-1; // Set ending index if (len == 2) //for two character string pal[i][j] = (str[i] == str[j]); else //for string of more than two characters pal[i][j] = (str[i] == str[j]) && pal[i+1][j-1]; if (pal[i][j] == true) cut[i][j] = 0; else { cut[i][j] = INT_MAX; //initially set as infinity for (int k=i; k<=j-1; k++) cut[i][j] = min(cut[i][j], cut[i][k] + cut[k+1][j]+1); } } } return cut[0][n-1]; } int main() { string str= "ababbbabbababa"; cout << "Min cuts for Palindrome Partitioning is:" << minPalPartion(str); }
输出
Min cuts for Palindrome Partitioning is: 3
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