You can not select more than 25 topics
Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
This file contains ambiguous Unicode characters that may be confused with others in your current locale. If your use case is intentional and legitimate, you can safely ignore this warning. Use the Escape button to highlight these characters.
package class_2022_07_2_week ;
import java.util.HashMap ;
// 给定一个字符串 s, 计算 s 的 不同非空子序列 的个数
// 因为结果可能很大,所以返回答案需要对 10^9 + 7 取余 。
// 字符串的 子序列 是经由原字符串删除一些(也可能不删除)字符
// 但不改变剩余字符相对位置的一个新字符串。
// 本题来自大厂刷题班17节
// 但是为了讲述一个最新题目,不得不重提这个题
// 本题测试链接 : https://leetcode.com/problems/distinct-subsequences-ii/
public class Code01_DistinctSubseqValue {
public static int distinctSubseqII ( String s ) {
if ( s = = null | | s . length ( ) = = 0 ) {
return 0 ;
}
int m = 1000000007 ;
char [ ] str = s . toCharArray ( ) ;
// a -> 0 ->
// b -> 1 ->
// c -> 2 ->
// z -> 25 ->
// count[i] = 0
int [ ] count = new int [ 26 ] ;
// { }
int all = 1 ; // 算空集
for ( char x : str ) {
// x
// 纯新增
// add = all - count[x]
// all += add
// count[x] + add
int add = ( all - count [ x - 'a' ] + m ) % m ;
all = ( all + add ) % m ;
count [ x - 'a' ] = ( count [ x - 'a' ] + add ) % m ;
}
// {} 去掉!
return all - 1 ;
}
public static int zuo ( String s ) {
if ( s = = null | | s . length ( ) = = 0 ) {
return 0 ;
}
int m = 1000000007 ;
char [ ] str = s . toCharArray ( ) ;
HashMap < Character , Integer > map = new HashMap < > ( ) ;
int all = 1 ; // 一个字符也没遍历的时候,有空集
for ( char x : str ) {
int newAdd = all ;
// int curAll = all + newAdd - (map.containsKey(x) ? map.get(x) : 0);
int curAll = all ;
curAll = ( curAll + newAdd ) % m ;
curAll = ( curAll - ( map . containsKey ( x ) ? map . get ( x ) : 0 ) + m ) % m ;
all = curAll ;
map . put ( x , newAdd ) ;
}
return all ;
}
public static void main ( String [ ] args ) {
String s = "bccaccbaabbc" ;
System . out . println ( distinctSubseqII ( s ) + 1 ) ;
System . out . println ( zuo ( s ) ) ;
}
}