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Commit7462d41

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add a solution for 25
1 parentd5901a3 commit7462d41

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2 files changed

+70
-9
lines changed

2 files changed

+70
-9
lines changed

‎src/main/java/com/fishercoder/solutions/_25.java

Lines changed: 53 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -84,4 +84,57 @@ public ListNode reverseKGroup(ListNode head, int k) {
8484
}
8585
}
8686

87+
publicstaticclassSolution3 {
88+
/**
89+
* My completely original solution on 10/25/2021. Beats 100% submissions on LeetCode in runtime.
90+
* Again, using a pen and paper to visualize the process helps a lot!
91+
* My helper function returns two nodes: reversed node head and the starting node for the next reversal.
92+
*/
93+
publicListNodereverseKGroup(ListNodehead,intk) {
94+
ListNodepre =newListNode(-1);
95+
pre.next =head;
96+
ListNodetmp =pre;
97+
ListNodecurr =head;
98+
ListNode[]result =newListNode[]{null,curr};
99+
do {
100+
result =reverseKGroupHelper(result[1],k);
101+
if (result[0] ==result[1]) {
102+
tmp.next =result[0];
103+
returnpre.next;
104+
}else {
105+
tmp.next =result[0];
106+
while (tmp.next !=null) {
107+
tmp =tmp.next;
108+
}
109+
}
110+
}while (true);
111+
}
112+
113+
privateListNode[]reverseKGroupHelper(ListNodehead,intk) {
114+
intoriginalK =k;
115+
ListNodetmp =head;
116+
while (tmp !=null) {
117+
tmp =tmp.next;
118+
k--;
119+
}
120+
if (k >0) {
121+
returnnewListNode[]{head,head};
122+
}else {
123+
tmp =head;
124+
k =originalK;
125+
ListNodeprev =null;
126+
while (tmp !=null) {
127+
ListNodenext =tmp.next;
128+
tmp.next =prev;
129+
prev =tmp;
130+
tmp =next;
131+
k--;
132+
if (k ==0) {
133+
returnnewListNode[]{prev,tmp};
134+
}
135+
}
136+
returnnull;
137+
}
138+
}
139+
}
87140
}

‎src/test/java/com/fishercoder/_25Test.java

Lines changed: 17 additions & 9 deletions
Original file line numberDiff line numberDiff line change
@@ -9,31 +9,39 @@
99
importstaticorg.junit.Assert.assertEquals;
1010

1111
publicclass_25Test {
12-
privatestatic_25.Solution1test;
13-
privatestatic_25.Solution2test2;
14-
privatestaticListNodeactual;
12+
privatestatic_25.Solution1solution1;
13+
privatestatic_25.Solution2solution2;
14+
privatestatic_25.Solution3solution3;
1515
privatestaticListNodeexpected;
1616
privatestaticListNodehead;
17+
privatestaticintk;
1718

1819
@BeforeClass
1920
publicstaticvoidsetup() {
20-
test =new_25.Solution1();
21-
test2 =new_25.Solution2();
21+
solution1 =new_25.Solution1();
22+
solution2 =new_25.Solution2();
23+
solution3 =new_25.Solution3();
2224
}
2325

2426
@Test
2527
publicvoidtest1() {
2628
head =LinkedListUtils.contructLinkedList(newint[]{1,2,3,4,5});
27-
actual =test.reverseKGroup(head,2);
29+
k =2;
2830
expected =LinkedListUtils.contructLinkedList(newint[]{2,1,4,3,5});
29-
assertEquals(actual,expected);
31+
assertEquals(expected,solution1.reverseKGroup(head,k));
3032
}
3133

3234
@Test
3335
publicvoidtest2() {
3436
head =LinkedListUtils.contructLinkedList(newint[]{1,2,3,4,5,6,7});
35-
actual =test2.reverseKGroup(head,4);
3637
expected =LinkedListUtils.contructLinkedList(newint[]{4,3,2,1,5,6,7});
37-
assertEquals(actual,expected);
38+
assertEquals(expected,solution2.reverseKGroup(head,4));
39+
}
40+
41+
@Test
42+
publicvoidtest3() {
43+
head =LinkedListUtils.contructLinkedList(newint[]{1,2,3,4,5,6,7});
44+
expected =LinkedListUtils.contructLinkedList(newint[]{4,3,2,1,5,6,7});
45+
assertEquals(expected,solution3.reverseKGroup(head,4));
3846
}
3947
}

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