Longest Common Subsequence

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Given two strings, find the longest common subsequence (LCS).

Your code should return the length of LCS.

Have you met this question in a real interview? Yes
Clarification
What's the definition of Longest Common Subsequence?

https://en.wikipedia.org/wiki/Longest_common_subsequence_problem
http://baike.baidu.com/view/2020307.htm
Example
For "ABCD" and "EDCA", the LCS is "A" (or "D", "C"), return 1.

For "ABCD" and "EACB", the LCS is "AC", return 2.
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状态方程时题意的转化, 通常要if, 遍历到当前状态时, 最后一个字母的情况与上一个或者上多个状态的关系

结果是最后的状态还是只是遍历到最后的状态求全局最优

Longest Increasing Subsequence

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public int longestCommonSubsequence(String A, String B) {
       // write your code here
       //state
       int m = A.length(), n = B.length();
       if (m == 0 || n == 0 || A == null || B == null) {
           return 0;
       }
       int[][] res = new int[m + 1][n + 1];
        
       //initialize
       for (int i = 0; i <= m; i++) {
           res[i][0] = 0;
       }
        for (int i = 0; i <= n; i++) {
           res[0][i] = 0;
       }
       //function
       for (int i = 1; i <= m; i++) {
           for (int j = 1; j <= n; j++) {
               if (A.charAt(i - 1) == B.charAt(j - 1)) {
                   res[i][j] = res[i - 1][j - 1] + 1;
               } else {
                   res[i][j] = Math.max(res[i - 1][j], res[i][j - 1]);
               }
           }
       }
       return res[m][n];
        
   }

  

posted @   apanda009  阅读(314)  评论(0编辑  收藏  举报
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