本文實(shí)例講述了java實(shí)現(xiàn)求兩個(gè)字符串最大公共子串的方法。分享給大家供大家參考，具體如下：
最近在項(xiàng)目工作中有一個(gè)關(guān)于文本對(duì)比的需求，經(jīng)過這段時(shí)間的學(xué)習(xí)，總結(jié)了這篇博客內(nèi)容：求兩個(gè)字符串的最大公共子串。
算法思想：基于圖計(jì)算兩字符串的公共子串。具體算法思想?yún)⒄障聢D：
輸入字符串S1：achmacmh 輸入字符串S2：macham
具體的實(shí)現(xiàn)代碼如下所示：
package cn.lulei.compare; import java.util.ArrayList; import java.util.Collections; import java.util.Comparator; import java.util.List; public class StringCompare { private int a; private int b; public String getMaxLengthCommonString(String s1, String s2) { if (s1 == null || s2 == null) { return null; } a = s1.length();//s1長(zhǎng)度做行 b = s2.length();//s2長(zhǎng)度做列 if(a== 0 || b == 0) { return ""; } //設(shè)置匹配矩陣 boolean [][] array = new boolean[a][b]; for (int i = 0; i < a; i++) { char c1 = s1.charAt(i); for (int j = 0; j < b; j++) { char c2 = s2.charAt(j); if (c1 == c2) { array[i][j] = true; } else { array[i][j] = false; } } } //求所有公因子字符串，保存信息為相對(duì)第二個(gè)字符串的起始位置和長(zhǎng)度 List<ChildString> childStrings = new ArrayList<ChildString>(); for (int i = 0; i < a; i++) { getMaxSort(i, 0, array, childStrings); } for (int i = 1; i < b; i++) { getMaxSort(0, i, array, childStrings); } //排序 sort(childStrings); if (childStrings.size() < 1) { return ""; } //返回最大公因子字符串 int max = childStrings.get(0).maxLength; StringBuffer sb = new StringBuffer(); for (ChildString s: childStrings) { if (max != s.maxLength) { break; } sb.append(s2.substring(s.maxStart, s.maxStart + s.maxLength)); sb.append("/n"); } return sb.toString(); } //排序，倒敘 private void sort(List<ChildString> list) { Collections.sort(list, new Comparator<ChildString>(){ public int compare(ChildString o1, ChildString o2) { return o2.maxLength - o1.maxLength; } }); } //求一條斜線上的公因子字符串 private void getMaxSort(int i, int j, boolean [][] array, List<ChildString> sortBean) { int length = 0; int start = j; for (; i < a && j < b; i++,j++) { if (array[i][j]) { length++; } else { sortBean.add(new ChildString(length, start)); length = 0; start = j + 1; } if (i == a-1 || j == b-1) { sortBean.add(new ChildString(length, start)); } } } //公因子類 class ChildString { int maxLength; int maxStart; ChildString(int maxLength, int maxStart){ this.maxLength = maxLength; this.maxStart = maxStart; } } /** * @param args */ public static void main(String[] args) { // TODO Auto-generated method stub System.out.println(new StringCompare().getMaxLengthCommonString("achmacmh", "macham")); } } 程序最終執(zhí)行結(jié)果是：
對(duì)于兩個(gè)文件的比對(duì)個(gè)人認(rèn)為可以參照這種算法思想（自己現(xiàn)在并為實(shí)現(xiàn)），在日后的博客中將會(huì)寫到。
上述實(shí)現(xiàn)過程中，用數(shù)組保存了所有的公共子串信息，然后排序取最大的子串，這種做法如果只是求最大子串的話，算法就不是很合理，因此做了如下修改，List只保存當(dāng)前計(jì)算中最大的子串，具體實(shí)現(xiàn)如下：
/** *@Description: 字符串比較 */ package com.lulei.test; import java.util.ArrayList; import java.util.List; public class StringCompare { private int a; private int b; private int maxLength = -1; public String getMaxLengthCommonString(String s1, String s2) { if (s1 == null || s2 == null) { return null; } a = s1.length();//s1長(zhǎng)度做行 b = s2.length();//s2長(zhǎng)度做列 if(a== 0 || b == 0) { return ""; } //設(shè)置匹配矩陣 boolean [][] array = new boolean[a][b]; for (int i = 0; i < a; i++) { char c1 = s1.charAt(i); for (int j = 0; j < b; j++) { char c2 = s2.charAt(j); if (c1 == c2) { array[i][j] = true; } else { array[i][j] = false; } } } //求所有公因子字符串，保存信息為相對(duì)第二個(gè)字符串的起始位置和長(zhǎng)度 List<ChildString> childStrings = new ArrayList<ChildString>(); for (int i = 0; i < a; i++) { getMaxSort(i, 0, array, childStrings); } for (int i = 1; i < b; i++) { getMaxSort(0, i, array, childStrings); } StringBuffer sb = new StringBuffer(); for (ChildString s: childStrings) { sb.append(s2.substring(s.maxStart, s.maxStart + s.maxLength)); sb.append("/n"); } return sb.toString(); } //求一條斜線上的公因子字符串 private void getMaxSort(int i, int j, boolean [][] array, List<ChildString> sortBean) { int length = 0; int start = j; for (; i < a && j < b; i++,j++) { if (array[i][j]) { length++; } else { //直接add，保存所有子串，下面的判斷，只保存當(dāng)前最大的子串 //sortBean.add(new ChildString(length, start)); if (length == maxLength) { sortBean.add(new ChildString(length, start)); } else if (length > maxLength) { sortBean.clear(); maxLength = length; sortBean.add(new ChildString(length, start)); } length = 0; start = j + 1; } if (i == a-1 || j == b-1) { //直接add，保存所有子串，下面的判斷，只保存當(dāng)前最大的子串 //sortBean.add(new ChildString(length, start)); if (length == maxLength) { sortBean.add(new ChildString(length, start)); } else if (length > maxLength) { sortBean.clear(); maxLength = length; sortBean.add(new ChildString(length, start)); } } } } //公因子類 class ChildString { int maxLength; int maxStart; ChildString(int maxLength, int maxStart){ this.maxLength = maxLength; this.maxStart = maxStart; } } /** * @param args */ public static void main(String[] args) { // TODO Auto-generated method stub System.out.println(new StringCompare().getMaxLengthCommonString("abcdef", "defabc")); } } 感謝閱讀，希望能幫助到大家，謝謝大家對(duì)本站的支持！
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