该程序完成在两个字符串中寻找最长公共子串，如果这样的字符串有多个，则将它们全部找出来，它在最坏情况下的复杂度为O(m*n).-the procedure is completed in two for the longest string of public substrings, if such a number of strings, will they all find out in the worst of the complexity of O (n* m).