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Commit 26bd72f

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author
kaidul
committed
After a long time..
1 parent 1ac64e3 commit 26bd72f

22 files changed

+376
-202
lines changed

‎source-code/Combinations.cpp

+28-1
Original file line numberDiff line numberDiff line change
@@ -19,4 +19,31 @@ class Solution {
1919
combineUtils(1, n, k, solution, result);
2020
return result;
2121
}
22-
};
22+
};
23+
24+
// Alternatives
25+
class Solution {
26+
public:
27+
void combineUtils(int idx, int n, int k, vector<int> &solution, vector<vector<int> > &result) {
28+
if(idx > n or solution.size() == k) {
29+
if(solution.size() == k)
30+
result.push_back(solution);
31+
return;
32+
}
33+
if(solution.size() < k) {
34+
solution.push_back(idx);
35+
combineUtils(idx + 1, n, k, solution, result);
36+
solution.pop_back();
37+
}
38+
39+
combineUtils(idx + 1, n, k, solution, result);
40+
}
41+
42+
vector<vector<int> > combine(int n, int k) {
43+
vector<vector<int> > result;
44+
vector<int> solution;
45+
if(k == 0 or n == 0) return result;
46+
combineUtils(1, n, k, solution, result);
47+
return result;
48+
}
49+
};

‎source-code/Convert_Sorted_List_to_Binary_Search_Tree.cpp

+2-2
Original file line numberDiff line numberDiff line change
@@ -23,7 +23,7 @@ class Solution {
2323
}
2424
ListNode *slow = head, *fast = head->next;
2525
ListNode *tail = nullptr;
26-
while(fast) {
26+
while(fast and fast->next) {
2727
fast = fast->next;
2828
tail = slow;
2929
slow = slow->next;
@@ -43,4 +43,4 @@ class Solution {
4343
TreeNode *sortedListToBST(ListNode *head) {
4444
return sortedListToBSTUtils(head);
4545
}
46-
};
46+
};

‎source-code/Count_and_Say.cpp

+8-12
Original file line numberDiff line numberDiff line change
@@ -5,21 +5,17 @@ class Solution {
55
if(n == 0) return result;
66
result = "1";
77
while(--n) {
8-
char prev = 'x';
9-
int count = 0;
108
string tmp = "";
11-
for(int i = 0; i < result.length(); ++i) {
12-
if(prev != 'x' and prev != result[i]) {
13-
tmp += (char)(count + '0');
14-
tmp += prev;
15-
prev = result[i];
16-
count = 0;
9+
for(int i = 0; i < result.length(); i++) {
10+
int count = 1;
11+
char digit = result[i];
12+
while(i + 1 < result.length() and result[i] == result[i + 1]) {
13+
i++;
14+
count++;
1715
}
18-
if(prev == 'x') prev = result[i];
19-
count++;
16+
tmp += char(count + '0');
17+
tmp += digit;
2018
}
21-
tmp += (char)(count + '0');
22-
tmp += prev;
2319
result = tmp;
2420
}
2521
return result;

‎source-code/Decode_Ways.cpp

+24-3
Original file line numberDiff line numberDiff line change
@@ -14,11 +14,33 @@ class Solution {
1414
}
1515
return true;
1616
}
17+
18+
int numDecodingsUtil(string s, int indx, vector<int>& dp) {
19+
if(indx == (int)s.length()) {
20+
return 1;
21+
}
22+
if(dp[indx] != -1) {
23+
return dp[indx];
24+
}
25+
int ret = 0;
26+
if(s[indx] != '0') {
27+
ret += numDecodingsUtil(s, indx + 1, dp);
28+
}
29+
if(indx + 1 < s.length() and valid(s.substr(indx, 2))) {
30+
ret += numDecodingsUtil(s, indx + 2, dp);
31+
}
32+
33+
return dp[indx] = ret;
34+
}
1735

18-
int numDecodings(string s) {
36+
int numDecodings(string s) {
1937
if (s.empty()) {
2038
return 0;
2139
}
40+
// recursive
41+
// vector<int> dp(s.size(), -1);
42+
// return numDecodingsUtil(s, 0, dp);
43+
2244
vector<int> dp(s.size(), 0);
2345
if (s[0] != '0') {
2446
dp[0] = 1;
@@ -33,7 +55,6 @@ class Solution {
3355
dp[1]++;
3456
}
3557

36-
//DP
3758
for (int i = 2; i < s.size(); i++) {
3859
if (s[i] != '0') {
3960
dp[i] += dp[i - 1];
@@ -45,4 +66,4 @@ class Solution {
4566

4667
return dp[s.size() - 1];
4768
}
48-
};
69+
};

‎source-code/Flatten_Binary_Tree_to_Linked_List.cpp

+8-7
Original file line numberDiff line numberDiff line change
@@ -9,18 +9,19 @@
99
*/
1010
class Solution {
1111
public:
12-
void flatten(TreeNode *root) {
12+
void flatten(TreeNode* root) {
1313
while(root) {
1414
if(root->left) {
15-
TreeNode *pre = root->left;
16-
while(pre->right) {
17-
pre = pre->right;
18-
}
19-
pre->right = root->right;
15+
TreeNode* right = root->right;
2016
root->right = root->left;
2117
root->left = nullptr;
18+
TreeNode* left = root->right;
19+
while(left->right) {
20+
left = left->right;
21+
}
22+
left->right = right;
2223
}
2324
root = root->right;
2425
}
2526
}
26-
};
27+
};

‎source-code/Gas_Station.cpp

+4-3
Original file line numberDiff line numberDiff line change
@@ -4,16 +4,17 @@ class Solution {
44
int n = (int) gas.size();
55
for(int i = 0; i < n; ++i) {
66
bool flag = true;
7-
for(int j = i, tank = 0; j < n + i and flag; ++j) {
7+
for(int j = i, tank = 0; j < n + i; ++j) {
88
int idx = j % n;
99
tank += gas[idx];
1010
tank -= cost[idx];
1111
if(tank < 0) {
1212
flag = false;
13+
break;
1314
}
1415
}
15-
if(flag) return j;
16+
if(flag) return i;
1617
}
1718
return -1;
1819
}
19-
};
20+
};

‎source-code/Goat_Latin.cpp

+41
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,41 @@
1+
class Solution {
2+
bool isVowel(char ch) {
3+
switch(tolower(ch)) {
4+
case 'a':
5+
case 'e':
6+
case 'i':
7+
case 'o':
8+
case 'u':
9+
return true;
10+
default:
11+
return false;
12+
}
13+
}
14+
public:
15+
string toGoatLatin(string S) {
16+
if(S.empty()) return S;
17+
int start = 0;
18+
string result;
19+
string suffix = "a";
20+
while(start < S.length()) {
21+
int end = S.find(' ', start);
22+
if(end == string::npos) {
23+
end = (int)S.length();
24+
}
25+
string word = S.substr(start, end - start);
26+
if(isVowel(word[0])) {
27+
word += "ma";
28+
} else {
29+
word += word[0];
30+
word += "ma";
31+
word = word.substr(1);
32+
}
33+
word += suffix;
34+
result += word;
35+
result += ' ';
36+
suffix += 'a';
37+
start = end + 1;
38+
}
39+
return result.substr(0, result.length() - 1); // or return result.erase(result.length() - 1, 1);
40+
}
41+
};

‎source-code/Longest_Consecutive_Sequence.cpp

+2-2
Original file line numberDiff line numberDiff line change
@@ -29,6 +29,6 @@ class Solution {
2929
result = max(result, seqLen);
3030
}
3131

32-
return res;
32+
return result;
3333
}
34-
};
34+
};

‎source-code/Longest_Valid_Parenthesis.cpp

+24
Original file line numberDiff line numberDiff line change
@@ -1,4 +1,28 @@
11
class Solution {
2+
public:
3+
int longestValidParentheses(string s) {
4+
stack<int> Stack;
5+
int result = 0;
6+
Stack.push(-1);
7+
for(int i = 0; i < (int)s.length(); i++) {
8+
if(s[i] == '(') {
9+
Stack.push(i);
10+
} else {
11+
if(Stack.size() == 1 or s[Stack.top()] != '(') {
12+
Stack.push(i);
13+
} else {
14+
Stack.pop();
15+
result = max(result, i - Stack.top());
16+
}
17+
}
18+
}
19+
20+
return result;
21+
}
22+
};
23+
24+
// Another way (slightly different)
25+
class Solution {
226
public:
327
int longestValidParentheses(string s) {
428
stack <int> Stack;

‎source-code/Merge_Sorted_Array.cpp

+16-11
Original file line numberDiff line numberDiff line change
@@ -2,13 +2,14 @@ class Solution {
22
public:
33
// AC but Extra space : O(m)
44
/*
5-
void merge(int A[], int m, int B[], int n) {
6-
int tmp[m];
7-
memcpy(tmp, A, m * sizeof(int));
5+
void merge(vector<int>& A, int m, vector<int>& B, int n) {
6+
vector<int> tmp(A);
87
int k = 0, i = 0, j = 0;
98
while(i < m and j < n) {
10-
if(tmp[i] <= B[j]) A[k++] = tmp[i++];
11-
else A[k++] = B[j++];
9+
if(tmp[i] <= B[j])
10+
A[k++] = tmp[i++];
11+
else
12+
A[k++] = B[j++];
1213
}
1314
while(i < m) {
1415
A[k++] = tmp[i++];
@@ -18,13 +19,17 @@ class Solution {
1819
}
1920
}
2021
*/
22+
23+
2124

22-
void merge(int A[], int m, int B[], int n) {
23-
int count = m + n - 1;
25+
void merge(vector<int>& nums1, int m, vector<int>& nums2, int n) {
26+
int k = m + n - 1;
2427
m--; n--;
25-
while (m >= 0 and n >= 0) {
26-
A[count--] = A[m] > B[n] ? A[m--] : B[n--];
28+
while(m >= 0 and n >= 0) {
29+
nums1[k--] = nums1[m] > nums2[n] ? nums1[m--] : nums2[n--];
30+
}
31+
while(n >= 0) {
32+
nums1[k--] = nums2[n--];
2733
}
28-
while (n >= 0) { A[count--] = B[n--]; }
2934
}
30-
};
35+
};

‎source-code/Reorder_List.cpp

+41-31
Original file line numberDiff line numberDiff line change
@@ -7,41 +7,51 @@
77
* };
88
*/
99
class Solution {
10-
public:
11-
void reorderList(ListNode *head) {
12-
if(!head) { return; }
13-
ListNode *slow = head, *fast = nullptr;
14-
if(head->next == nullptr) { return; }
15-
fast = head->next;
16-
if(head->next->next == nullptr) { return; }
17-
if(fast) while(fast->next) {
18-
fast = fast->next;
10+
ListNode* findMid(ListNode* head) {
11+
ListNode* slow = head;
12+
ListNode* fast = head;
13+
fast = fast->next;
14+
while(fast->next) {
1915
slow = slow->next;
20-
if(fast->next) fast = fast->next;
16+
fast = fast->next;
17+
if(fast->next) {
18+
fast = fast->next;
19+
}
2120
}
22-
ListNode *tmp = slow->next;
23-
slow->next = nullptr;
24-
ListNode *head2 = tmp;
25-
tmp = tmp->next;
26-
head2->next = nullptr;
27-
while(tmp) {
28-
ListNode *tmp2 = tmp->next;
29-
tmp->next = head2;
30-
head2 = tmp;
31-
tmp = tmp2;
21+
return slow;
22+
}
23+
24+
ListNode* reverseList(ListNode* head) {
25+
ListNode* iter = head;
26+
ListNode* prev = nullptr;
27+
while(iter) {
28+
ListNode* next = iter->next;
29+
iter->next = prev;
30+
prev = iter;
31+
head = iter;
32+
iter = next;
3233
}
33-
ListNode *backup = head, *iter = head;
34-
head = head->next;
34+
return head;
35+
}
36+
37+
public:
38+
void reorderList(ListNode* head) {
39+
if(!head or !head->next or !head->next->next) {
40+
return;
41+
}
42+
ListNode* mid = findMid(head);
43+
ListNode* head2 = mid->next;
44+
mid->next = nullptr;
45+
head2 = reverseList(head2);
46+
ListNode* backup = head;
3547
while(head2) {
36-
iter->next = head2;
37-
iter = iter->next;
38-
head2 = head2->next;
39-
40-
if(head) {
41-
iter->next = head;
42-
iter = iter->next;
43-
head = head->next;
44-
}
48+
ListNode* next = head->next;
49+
head->next = head2;
50+
ListNode* next2 = head2->next;
51+
head2->next = next;
52+
53+
head = next;
54+
head2 = next2;
4555
}
4656
head = backup;
4757
}

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