算法 day9

長按鍵入

class Solution {
public:
    bool isLongPressedName(string name, string typed) {
        int p1 = 0;
        int p2 = 0;
        int len1 = name.length();
        int len2 = typed.length();
        while(p1<len1&&p1<len2)
        {
            char nowc = name[p1];
            int c1 = 0;
            while(name[p1] == nowc)
            {
                p1++;
                c1++;
            }
            int c2 = 0;
            while(typed[p2] == nowc)
            {
                p2++;
                c2++;
            }
            if(c1>c2)return false;
        }

        if(p1==len1&&p2==len2)return true;
        else return false;
    }
};

牆與門

多源bfs重寫

class Solution {
public:
    void wallsAndGates(vector<vector<int>>& rooms) {
        queue<pair<int,int>>q;
        int n = rooms.size();
        if(!n)return;
        int m = rooms[0].size();
        int inf = 2147483647;
        for(int i=0;i<n;i++)
        {
            for(int j=0;j<m;j++)
            {
                if(rooms[i][j]==0)q.push({i,j});
            }
        }
        while(!q.empty())
        {
            int dx[] = {-1,1,0,0};
            int dy[] = {0,0,-1,1};
            pair<int,int>tmp = q.front();
            q.pop();
            for(int k=0;k<4;k++)
            {
                int newx = tmp.first+dx[k];
                int newy = tmp.second+dy[k];
                if(newx>=0&&newx<n&&newy>=0&&newy<m&&rooms[newx][newy]==inf)
                {
                    rooms[newx][newy] = rooms[tmp.first][tmp.second]+1;
                    q.push({newx,newy});
                }
            } 
        }
    }
};

島嶼數量

class Solution {
public:
    int numIslands(vector<vector<char>>& grid) {
        int n = grid.size();
        if(!n)return 0;
        int m = grid[0].size();
        queue<pair<int,int>>q;
        int ccount = 0;
        for(int i=0;i<n;i++)
        {
            for(int j=0;j<m;j++)
            {
                if(grid[i][j] == '1')
                {
                    grid[i][j] = '0';
                    q.push({i,j});
                    ccount++;
                    while(!q.empty())
                    {
                        pair<int,int>tmp = q.front();
                        q.pop();
                        int dx[]={-1,1,0,0};
                        int dy[]={0,0,-1,1};
                        for(int k=0;k<4;k++)
                        {
                            int newx = tmp.first+dx[k];
                            int newy = tmp.second+dy[k];
                            if(newx>=0&&newx<n&&newy>=0&&newy<m&&grid[newx][newy]=='1')
                            {
                                grid[newx][newy] ='0';
                                q.push({newx,newy});
                            }
                        }
                    }
                    
                }
            }
        }
        return ccount;
    }
};

 兩個二叉搜索樹節點最深公共祖先

/**
 * 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:
    TreeNode* lowestCommonAncestor(TreeNode* root, TreeNode* p, TreeNode* q) {
        int pval = p->val;
        int qval = q->val;
        int rootval = root->val;
        printf("%d\n",rootval);
        if(root==NULL)return root;
        if((qval-rootval)*(pval-rootval)<=0)
            return root;
        if(qval>rootval)
            return lowestCommonAncestor(root->right,p,q);
        if(qval<rootval)
            return lowestCommonAncestor(root->left,p,q);
        return root;
    }
};

 兩個二叉樹節點最深公共祖先

/**
 * 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:
    TreeNode* lowestCommonAncestor(TreeNode* root, TreeNode* p, TreeNode* q) {
        if(root == NULL || p==root || q==root)
        return root;

        TreeNode* left = lowestCommonAncestor(root->left,p,q);
        TreeNode* right = lowestCommonAncestor(root->right,p,q);

        if(left !=NULL && right!=NULL)return root;
        if(left == NULL)return right;
        else return left;
    }
};

 機器人

class Solution {
public:
    int uniquePaths(int m, int n) {
        int dp[m+1][n+1];
        //求dp[m][n]
        for(int i=1;i<=m;i++)
        {
            for(int j=1;j<=n;j++)
            {
                if(i==1||j==1)
                {
                    dp[i][j]=1;
                }
                else
                {
                    dp[i][j]=0;
                }
            }
        }

        for(int i=2;i<=m;i++)
        {
            for(int j=2;j<=n;j++)
            {
                dp[i][j]=dp[i-1][j]+dp[i][j-1];
            }
        }
        return dp[m][n];
    }
};

最小路徑和

class Solution {
public:
    int minPathSum(vector<vector<int>>& grid) {
        int m = grid.size();
        if(!m)return 0;

        int n = grid[0].size();

        int dp[m][n];
        dp[0][0] = grid[0][0];
        for(int i=1;i<m;i++)
        {
            dp[i][0] = dp[i-1][0]+grid[i][0]; 
        }
        for(int j=1;j<n;j++)
        {
            dp[0][j] = dp[0][j-1]+grid[0][j];
        }

        for(int i=1;i<m;i++)
        {
            for(int j=1;j<n;j++)
            {
                dp[i][j] = grid[i][j]+min(dp[i-1][j],dp[i][j-1]);
            }
        }
        return dp[m-1][n-1];
    }
};