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lines changed Original file line number Diff line number Diff line change 4949
5050<!-- 这里可写通用的实现逻辑 -->
5151
52+ ** 方法一：双指针**
53+
54+ 我们可以使用双指针的方法，用指针 $j$ 指向目标字符串 ` target ` ，然后遍历源字符串 ` source ` ，用指针 $i$ 指向源字符串 ` source ` ，如果 $source[ i] = target[ j] $，则 $i$ 和 $j$ 同时向后移动一位，否则只移动 $i$ 指针。当指针 $i$ 和 $j$ 都到达字符串末尾时，如果没有找到相等的字符，则返回 $-1$，否则子序列数量加一，然后将指针 $i$ 置为 $0$，继续遍历。
55+
56+ 遍历结束后，返回子序列数量即可。
57+
58+ 时间复杂度 $O(m \times n)$，空间复杂度 $O(1)$。其中 $m$ 和 $n$ 分别为字符串 ` source ` 和 ` target ` 的长度。
59+
5260<!-- tabs:start -->
5361
5462### ** Python3**
5563
5664<!-- 这里可写当前语言的特殊实现逻辑 -->
5765
5866``` python
59-
67+ class Solution :
68+ def shortestWay (self source : str , target : str ) -> int :
69+ def f (i , j ):
70+ while i < m and j < n:
71+ if source[i] == target[j]:
72+ j += 1
73+ i += 1
74+ return j
75+
76+ m, n = len (source), len (target)
77+ ans = j = 0
78+ while j < n:
79+ k = f(0 , j)
80+ if k == j:
81+ return - 1
82+ j = k
83+ ans += 1
84+ return ans
6085```
6186
6287### ** Java**
6388
6489<!-- 这里可写当前语言的特殊实现逻辑 -->
6590
6691``` java
92+ class Solution {
93+ public int shortestWay (String source , String target ) {
94+ int m = source. length(), n = target. length();
95+ int ans = 0 , j = 0 ;
96+ while (j < n) {
97+ int i = 0 ;
98+ boolean ok = false ;
99+ while (i < m && j < n) {
100+ if (source. charAt(i) == target. charAt(j)) {
101+ ok = true ;
102+ ++ j;
103+ }
104+ ++ i;
105+ }
106+ if (! ok) {
107+ return - 1 ;
108+ }
109+ ++ ans;
110+ }
111+ return ans;
112+ }
113+ }
114+ ```
115+
116+ ### ** C++**
117+
118+ ``` cpp
119+ class Solution {
120+ public:
121+ int shortestWay(string source, string target) {
122+ int m = source.size(), n = target.size();
123+ int ans = 0, j = 0;
124+ while (j < n) {
125+ int i = 0;
126+ bool ok = false;
127+ while (i < m && j < n) {
128+ if (source[ i] == target[ j] ) {
129+ ok = true;
130+ ++j;
131+ }
132+ ++i;
133+ }
134+ if (!ok) {
135+ return -1;
136+ }
137+ ++ans;
138+ }
139+ return ans;
140+ }
141+ };
142+ ```
67143
144+ ### **Go**
145+
146+ ```go
147+ func shortestWay(source string, target string) int {
148+ m, n := len(source), len(target)
149+ ans, j := 0, 0
150+ for j < n {
151+ ok := false
152+ for i := 0; i < m && j < n; i++ {
153+ if source[i] == target[j] {
154+ ok = true
155+ j++
156+ }
157+ }
158+ if !ok {
159+ return -1
160+ }
161+ ans++
162+ }
163+ return ans
164+ }
68165```
69166
70167### ** ...**
Original file line number Diff line number Diff line change 4848### ** Python3**
4949
5050``` python
51-
51+ class Solution :
52+ def shortestWay (self source : str , target : str ) -> int :
53+ def f (i , j ):
54+ while i < m and j < n:
55+ if source[i] == target[j]:
56+ j += 1
57+ i += 1
58+ return j
59+
60+ m, n = len (source), len (target)
61+ ans = j = 0
62+ while j < n:
63+ k = f(0 , j)
64+ if k == j:
65+ return - 1
66+ j = k
67+ ans += 1
68+ return ans
5269```
5370
5471### ** Java**
5572
5673``` java
74+ class Solution {
75+ public int shortestWay (String source , String target ) {
76+ int m = source. length(), n = target. length();
77+ int ans = 0 , j = 0 ;
78+ while (j < n) {
79+ int i = 0 ;
80+ boolean ok = false ;
81+ while (i < m && j < n) {
82+ if (source. charAt(i) == target. charAt(j)) {
83+ ok = true ;
84+ ++ j;
85+ }
86+ ++ i;
87+ }
88+ if (! ok) {
89+ return - 1 ;
90+ }
91+ ++ ans;
92+ }
93+ return ans;
94+ }
95+ }
96+ ```
97+
98+ ### ** C++**
99+
100+ ``` cpp
101+ class Solution {
102+ public:
103+ int shortestWay(string source, string target) {
104+ int m = source.size(), n = target.size();
105+ int ans = 0, j = 0;
106+ while (j < n) {
107+ int i = 0;
108+ bool ok = false;
109+ while (i < m && j < n) {
110+ if (source[ i] == target[ j] ) {
111+ ok = true;
112+ ++j;
113+ }
114+ ++i;
115+ }
116+ if (!ok) {
117+ return -1;
118+ }
119+ ++ans;
120+ }
121+ return ans;
122+ }
123+ };
124+ ```
57125
126+ ### **Go**
127+
128+ ```go
129+ func shortestWay(source string, target string) int {
130+ m, n := len(source), len(target)
131+ ans, j := 0, 0
132+ for j < n {
133+ ok := false
134+ for i := 0; i < m && j < n; i++ {
135+ if source[i] == target[j] {
136+ ok = true
137+ j++
138+ }
139+ }
140+ if !ok {
141+ return -1
142+ }
143+ ans++
144+ }
145+ return ans
146+ }
58147```
59148
60149### ** ...**
Original file line number Diff line number Diff line change 1+ class Solution {
2+ public:
3+ int shortestWay (string source, string target) {
4+ int m = source.size (), n = target.size ();
5+ int ans = 0 , j = 0 ;
6+ while (j < n) {
7+ int i = 0 ;
8+ bool ok = false ;
9+ while (i < m && j < n) {
10+ if (source[i] == target[j]) {
11+ ok = true ;
12+ ++j;
13+ }
14+ ++i;
15+ }
16+ if (!ok) {
17+ return -1 ;
18+ }
19+ ++ans;
20+ }
21+ return ans;
22+ }
23+ };
Original file line number Diff line number Diff line change 1+ func shortestWay (source string , target string ) int {
2+ m , n := len (source ), len (target )
3+ ans , j := 0 , 0
4+ for j < n {
5+ ok := false
6+ for i := 0 ; i < m && j < n ; i ++ {
7+ if source [i ] == target [j ] {
8+ ok = true
9+ j ++
10+ }
11+ }
12+ if ! ok {
13+ return - 1
14+ }
15+ ans ++
16+ }
17+ return ans
18+ }
Original file line number Diff line number Diff line change 1+ class Solution {
2+ public int shortestWay (String source , String target ) {
3+ int m = source .length (), n = target .length ();
4+ int ans = 0 , j = 0 ;
5+ while (j < n ) {
6+ int i = 0 ;
7+ boolean ok = false ;
8+ while (i < m && j < n ) {
9+ if (source .charAt (i ) == target .charAt (j )) {
10+ ok = true ;
11+ ++j ;
12+ }
13+ ++i ;
14+ }
15+ if (!ok ) {
16+ return -1 ;
17+ }
18+ ++ans ;
19+ }
20+ return ans ;
21+ }
22+ }
Original file line number Diff line number Diff line change 1+ class Solution :
2+ def shortestWay (self , source : str , target : str ) -> int :
3+ def f (i , j ):
4+ while i < m and j < n :
5+ if source [i ] == target [j ]:
6+ j += 1
7+ i += 1
8+ return j
9+
10+ m , n = len (source ), len (target )
11+ ans = j = 0
12+ while j < n :
13+ k = f (0 , j )
14+ if k == j :
15+ return - 1
16+ j = k
17+ ans += 1
18+ return ans
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