Given a string S and a string T, count the number of distinct subsequences of S which equals T. A subsequence of a string is a new string which is formed from the original string by deleting some (can be none) of the characters without disturbing the…

［抄题］: 给出字符串S和字符串T,计算S的不同的子序列中T出现的个数. 子序列字符串是原始字符串通过删除一些(或零个)产生的一个新的字符串,并且对剩下的字符的相对位置没有影响.(比如,“ACE”是“ABCDE”的子序列字符串,而“AEC”不是). Here is an example:S = "rabbbit", T = "rabbit" Return 3. ［思维问题］: ［一句话思路］: 由于要查找T.最后一位相同时可以同时删,不相同时只能删S,不能多删除T.…

问题 给出字符串S和T,计算S中为T的不同的子序列的个数. 一个字符串的子序列是一个由该原始字符串通过删除一些字母(也可以不删)但是不改变剩下字母的相对顺序产生的一个新字符串.如,ACE是ABCDE的一个子序列,但是AEC不是. 这里有一个例子: S＝“rabbbit”,T＝“rabbit” 返回值应为3 初始思路 要找出子序列的个数,首先要有找出S中为T的子序列的方法.T是S的子序列,首先其每一个字母肯定会在S中出现,通过遍历T的每一个字母即可完成这个检查.而根据不能乱序的要求,下一个字母在S…

Given a string S and a string T, count the number of distinct subsequences of T in S. A subsequence of a string is a new string which is formed from the original string by deleting some (can be none) of the characters without disturbing the relative…

Given a string S, count the number of distinct, non-empty subsequences of S . Since the result may be large, return the answer modulo 10^9 + 7. Example 1: Input: "abc" Output: 7 Explanation: The 7 distinct subsequences are "a", "b…

Given a string S and a string T, count the number of distinct subsequences of S which equals T. A subsequence of a string is a new string which is formed from the original string by deleting some (can be none) of the characters without disturbing the…

引言 子序列和子字符串或者连续子集的不同之处在于,子序列不需要是原序列上连续的值. 对于子序列的题目,大多数需要用到DP的思想,因此,状态转移是关键. 这里摘录两个常见子序列问题及其解法. 例题1, 最长公共子序列 我们知道最长公共子串的求法,先温习一下,它的求法也是使用DP思想,对于 字符串s1 和字符串s2,令 m[i][j] 表示 s1上以s1[i]结尾的子串和s2上s2[j]结尾的子串的最长公共子串长度,因为公共子串必须是连续的,因此状态转移方程:m[i, j] = (s1[i] ==…

Given a string S and a string T, count the number of distinct subsequences ofT inS. A subsequence of a string is a new string which is formed from the original string by deleting some (can be none) of the characters without disturbing the relative po…

Given a string S and a string T, count the number of distinct subsequences of S which equals T. A subsequence of a string is a new string which is formed from the original string by deleting some (can be none) of the characters without disturbing the…

Given a string S and a string T, count the number of distinct subsequences of T in S. A subsequence of a string is a new string which is formed from the original string by deleting some (can be none) of the characters without disturbing the relative…