Weekly Contest 131
1021. Remove Outermost Parentheses
A valid parentheses string is either empty
("")
,"(" + A + ")"
, orA + B
, whereA
andB
are valid parentheses strings, and+
represents string concatenation. For example,""
,"()"
,"(())()"
, and"(()(()))"
are all valid parentheses strings.A valid parentheses string
S
is primitive if it is nonempty, and there does not exist a way to split it intoS = A+B
, withA
andB
nonempty valid parentheses strings.Given a valid parentheses string
S
, consider its primitive decomposition:S = P_1 + P_2 + ... + P_k
, whereP_i
are primitive valid parentheses strings.Return
S
after removing the outermost parentheses of every primitive string in the primitive decomposition ofS
.
Example 1:
Input: "(()())(())"
Output: "()()()"
Explanation:
The input string is "(()())(())", with primitive decomposition "(()())" + "(())".
After removing outer parentheses of each part, this is "()()" + "()" = "()()()".Example 2:
Input: "(()())(())(()(()))"
Output: "()()()()(())"
Explanation:
The input string is "(()())(())(()(()))", with primitive decomposition "(()())" + "(())" + "(()(()))".
After removing outer parentheses of each part, this is "()()" + "()" + "()(())" = "()()()()(())".Example 3:
Input: "()()"
Output: ""
Explanation:
The input string is "()()", with primitive decomposition "()" + "()".
After removing outer parentheses of each part, this is "" + "" = "".
Note:
S.length <= 10000
S[i]
is"("
or")"
S
is a valid parentheses string
Approach #1: Stack. [C++]
class Solution {
public:
string removeOuterParentheses(string S) {
stack<char> sta;
int left = 0, right = 0;
string ans = "";
for (int i = 0; i < S.length(); ++i) {
if (sta.empty()) {
right = i - 1;
if (right - left - 1 >= 2) {
string s = S.substr(left+1, right-left-1);
ans += s;
}
left = i;
sta.push(S[i]);
} else {
if (sta.top() == '(' && S[i] == ')') {
sta.pop();
} else {
sta.push(S[i]);
}
}
}
string s = S.substr(left+1, S.length()-left-2);
ans += s; return ans;
}
};
1022. Sum of Root To Leaf Binary Numbers
Given a binary tree, each node has value
0
or1
. Each root-to-leaf path represents a binary number starting with the most significant bit. For example, if the path is0 -> 1 -> 1 -> 0 -> 1
, then this could represent01101
in binary, which is13
.For all leaves in the tree, consider the numbers represented by the path from the root to that leaf.
Return the sum of these numbers.
Example 1:
Input: [1,0,1,0,1,0,1]
Output: 22
Explanation: (100) + (101) + (110) + (111) = 4 + 5 + 6 + 7 = 22
Note:
- The number of nodes in the tree is between
1
and1000
.- node.val is
0
or1
.- The answer will not exceed
2^31 - 1
.
Approach #1: [C++]
/**
* Definition for a binary tree node.
* struct TreeNode {
* int val;
* TreeNode *left;
* TreeNode *right;
* TreeNode(int x) : val(x), left(NULL), right(NULL) {}
* };
*/
class Solution {
public:
int sumRootToLeaf(TreeNode* root, int val = 0) {
const static int mod = 1000000007;
if (!root) return 0;
val = val * 2 + root->val;
return (root->left == root->right ? val : sumRootToLeaf(root->left, val) + sumRootToLeaf(root->right, val)) % mod;
}
};
1023. Camelcase Matching
A query word matches a given
pattern
if we can insert lowercase letters to the pattern word so that it equals thequery
. (We may insert each character at any position, and may insert 0 characters.)Given a list of
queries
, and apattern
, return ananswer
list of booleans, whereanswer[i]
is true if and only ifqueries[i]
matches thepattern
.
Example 1:
Input: queries = ["FooBar","FooBarTest","FootBall","FrameBuffer","ForceFeedBack"], pattern = "FB"
Output: [true,false,true,true,false]
Explanation:
"FooBar" can be generated like this "F" + "oo" + "B" + "ar".
"FootBall" can be generated like this "F" + "oot" + "B" + "all".
"FrameBuffer" can be generated like this "F" + "rame" + "B" + "uffer".Example 2:
Input: queries = ["FooBar","FooBarTest","FootBall","FrameBuffer","ForceFeedBack"], pattern = "FoBa"
Output: [true,false,true,false,false]
Explanation:
"FooBar" can be generated like this "Fo" + "o" + "Ba" + "r".
"FootBall" can be generated like this "Fo" + "ot" + "Ba" + "ll".Example 3:
Input: queries = ["FooBar","FooBarTest","FootBall","FrameBuffer","ForceFeedBack"], pattern = "FoBaT"
Output: [false,true,false,false,false]
Explanation:
"FooBarTest" can be generated like this "Fo" + "o" + "Ba" + "r" + "T" + "est".
Note:
1 <= queries.length <= 100
1 <= queries[i].length <= 100
1 <= pattern.length <= 100
- All strings consists only of lower and upper case English letters.
Approach #1: [C++]
class Solution {
public:
vector<bool> camelMatch(vector<string>& queries, string pattern) {
vector<bool> res;
for (int i = 0; i < queries.size(); ++i) {
res.push_back(judge(queries[i], pattern));
}
return res;
} private:
bool judge(string str, string pattern) {
int pnt = 0;
for (int i = 0; i < str.length(); ++i) {
if (str[i] == pattern[pnt]) pnt++;
else if (islower(str[i])) continue;
else return false;
}
return pnt == pattern.length();
}
};
1024. Video Stitching
You are given a series of video clips from a sporting event that lasted
T
seconds. These video clips can be overlapping with each other and have varied lengths.Each video clip
clips[i]
is an interval: it starts at timeclips[i][0]
and ends at timeclips[i][1]
. We can cut these clips into segments freely: for example, a clip[0, 7]
can be cut into segments[0, 1] + [1, 3] + [3, 7]
.Return the minimum number of clips needed so that we can cut the clips into segments that cover the entire sporting event (
[0, T]
). If the task is impossible, return-1
.
Example 1:
Input: clips = [[0,2],[4,6],[8,10],[1,9],[1,5],[5,9]], T = 10
Output: 3
Explanation:
We take the clips [0,2], [8,10], [1,9]; a total of 3 clips.
Then, we can reconstruct the sporting event as follows:
We cut [1,9] into segments [1,2] + [2,8] + [8,9].
Now we have segments [0,2] + [2,8] + [8,10] which cover the sporting event [0, 10].Example 2:
Input: clips = [[0,1],[1,2]], T = 5
Output: -1
Explanation:
We can't cover [0,5] with only [0,1] and [0,2].Example 3:
Input: clips = [[0,1],[6,8],[0,2],[5,6],[0,4],[0,3],[6,7],[1,3],[4,7],[1,4],[2,5],[2,6],[3,4],[4,5],[5,7],[6,9]], T = 9
Output: 3
Explanation:
We can take clips [0,4], [4,7], and [6,9].Example 4:
Input: clips = [[0,4],[2,8]], T = 5
Output: 2
Explanation:
Notice you can have extra video after the event ends.
Note:
1 <= clips.length <= 100
0 <= clips[i][0], clips[i][1] <= 100
0 <= T <= 100
Approach #1: [C++]
class Solution {
public:
int videoStitching(vector<vector<int>>& clips, int T) {
int n = clips.size();
sort(clips.begin(), clips.end(), [](vector<int>& u, vector<int>& v) {
return u[1] < v[1];
});
vector<int> dp(n+1, 0);
int ret = INF;
for (int i = 0; i < n; ++i) {
dp[i] = (clips[i][0] == 0) ? 1 : INF;
for (int j = 0; j < i; ++j) {
if (clips[j][1] >= clips[i][0]) {
dp[i] = min(dp[j] + 1, dp[i]);
}
}
}
for (int i = 0; i < n; ++i) {
if (clips[i][1] >= T)
ret = min(dp[i], ret);
} return (ret == INF) ? -1 : ret;
} private:
const int INF = 1 << 30;
};
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