LeetCode开心刷题二十天——32. Longest Valid Parentheses(Compare consider with 31)33. Search in Rotated Sorted Array38. Count and Say

32. Longest Valid Parentheses

Hard

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Given a string containing just the characters '(' and ')', find the length of the longest valid (well-formed) parentheses substring.

Example 1:

Input: "(()"
Output: 2
Explanation: The longest valid parentheses substring is "()"

Example 2:

Input: ")()())"
Output: 4
Explanation: The longest valid parentheses substring is "()()"

Accepted

200,042

Submissions

774,584

#include<stdio.h>
#include<iostream>
#include<vector>
#include<algorithm>
#include<stack>
#include<string>
#include<memory>
#include<memory.h>
#include<hash_map>
#include<map>
#include<set>
#include<unordered_map>
using namespace std;
class Solution {
public:
    int longestValidParentheses(string s) {
        stack<int> q;
        int start=0;
        int ans=0;
        for(int i=0;i<s.length();i++)
        {
            if(s[i]=='(')
                q.push(i);
            else
            {
                if(q.empty())
                    start=i+1;
                else
                {
                    int temp=q.top();q.pop();
                    //+1 is to add the first(
                    ans=max(ans,q.empty()?i-start+1:i-q.top());
                }

            }
        }
        return ans;

    }
};
int main()
{
    string res={"(())"};
    Solution s;
    int n;
    n=s.longestValidParentheses(res);
    cout<<n<<endl;
    return 0;
}

 

33. Search in Rotated Sorted Array

Medium

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Suppose an array sorted in ascending order is rotated at some pivot unknown to you beforehand.

(i.e., [0,1,2,4,5,6,7] might become [4,5,6,7,0,1,2]).

You are given a target value to search. If found in the array return its index, otherwise return -1.

You may assume no duplicate exists in the array.

Your algorithm's runtime complexity must be in the order of O(log n).

Example 1:

Input: nums = [4,5,6,7,0,1,2], target = 0
Output: 4

Example 2:

Input: nums = [4,5,6,7,0,1,2], target = 3
Output: -1

ATTENTION POINT：
please clarify > >= whether add = can cause largely difference in many situations
in this code if you not write l<=r ,not =,will cause a lot of problem

#include<stdio.h>
#include<iostream>
#include<vector>
#include<algorithm>
#include<stack>
#include<string>
#include<memory>
#include<memory.h>
#include<hash_map>
#include<map>
#include<set>
#include<unordered_map>
using namespace std;
class Solution {
public:
    int search(vector<int>& nums, int target) {
        int l=0,r=nums.size()-1;
        while(l<=r)
        {
            int mid=(l+r)/2;
            if(nums[mid]==target) return mid;
            if(nums[mid]<nums[r])
            {
                if(target>nums[mid]&&target<=nums[r])
                    l=mid+1;
                else
                    r=mid-1;

            }
            else
            {
                if(target>=nums[l]&&target<nums[mid])
                {
                    r=mid-1;
                }
                else
                {
                    l=mid+1;
                }
            }

        }
        return -1;
    }
};
int main()
{
    vector<int> nums={4,5,6,7,0,1,2};
    int target=0,res=0;
    Solution s;
    res=s.search(nums,target);
    cout<<res<<endl;
    return 0;
}

 

38. Count and Say

Easy

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The count-and-say sequence is the sequence of integers with the first five terms as following:

1.     1
2.     11
3.     21
4.     1211
5.     111221

1 is read off as "one 1" or 11.
11 is read off as "two 1s" or 21.
21 is read off as "one 2, then one 1" or 1211.

Given an integer n where 1 ≤ n ≤ 30, generate the nth term of the count-and-say sequence.

Note: Each term of the sequence of integers will be represented as a string.

 

Example 1:

Input: 1
Output: "1"

Example 2:

Input: 4
Output: "1211"

 ATTENTION:
1.for loop attention the begin and end;for(i=0/1;i</<=n;i++)
2.string has special action to solve,such as string+=a,then string add a behind it.
3.string number '3' and real number 3 the distance is '0',so it need to minus '0' before
it to add into calculation.

#include<stdio.h>
#include<iostream>
#include<vector>
#include<algorithm>
#include<stack>
#include<string>
#include<memory>
#include<memory.h>
#include<hash_map>
#include<map>
#include<set>
#include<unordered_map>
using namespace std;
class Solution {
public:
    string countAndSay(int n) {
        string ans="1";
        for(int i=1;i<n;i++)
        {
            ans=say(ans);
        }
        return ans;
    }
private:
    string say(const string& n)
    {
        string ans;
        int s=0,l=n.length();
        for(int e=1;e<=l;e++)
        {
            if(e==l||n[s]!=n[e])
            {
                int count=e-s;
                ans+='0'+count;
                ans+=n[s];
                s=e;
            }
        }
        return ans;
    }
};
int main()
{
    string res;
    Solution s;
    int n=4;
    res=s.countAndSay(n);
    cout<<res<<endl;
    return 0;
}