最長公共子串與最長公共子序列(動歸實現)
阿新 • • 發佈:2018-12-16
什麼是子序列?一個給定的序列的子序列,就是將給定序列中零個或多個元素去掉之後得到的結果。
什麼是子串?給定串中任意個連續的字元組成的子序列稱為該串的子串。(相對於子序列,子串是連續的)
如abcdef
acd是子序列。
bcd是子串。
最長公共子序列程式碼:
public static int str(String s1, String s2) { int len1 = s1.length(); int len2 = s2.length(); if (len1 == 0 || len2 == 0) { return 0; } int[][] num = new int[len1 + 1][len2 + 1]; for (int i = 0; i <= len1; i++) { num[i][0] = 0; } for (int i = 0; i <= len2; i++) { num[0][i] = 0; } for (int i = 1; i <= len1; i++) for (int j = 1; j <= len2; j++) { if (s1.charAt(i - 1) == s2.charAt(j - 1)) num[i][j] = num[i - 1][j - 1] + 1; else num[i][j] = Math.max(num[i - 1][j], num[i][j - 1]); } return num[len1][len2]; }
最長公共子串程式碼:
public static int str2(String s1, String s2) { int len1 = s1.length(); int len2 = s2.length(); if (len1 == 0 || len2 == 0) { return 0; } int[][] num = new int[len1 + 1][len2 + 1]; for (int i = 0; i <= len1; i++) { num[i][0] = 0; } for (int i = 0; i <= len2; i++) { num[0][i] = 0; } int res = 0; for (int i = 1; i <= len1; i++) for (int j = 1; j <= len2; j++) { if (s1.charAt(i - 1) == s2.charAt(j - 1)) num[i][j] = num[i - 1][j - 1] + 1; if (res < num[i][j]) res = num[i][j]; } return res; }