【LeetCode 热题 100】最小路径和 / 最长回文子串 / 最长公共子序列 / 编辑距离

class Solution {
public:
    int uniquePaths(int m, int n) {
        vector<vector<int>> dp(m + 1, vector<int>(n + 1));
        dp[0][1] = 1;
        for (int i = 1; i <= m; i++)
        {
            for (int j = 1; j <= n; j++)
            {
                dp[i][j] = dp[i - 1][j] + dp[i][j - 1];
            }
        }
        return dp[m][n];
    }
};

class Solution {
public:
    int minPathSum(vector<vector<int>>& grid) {
        int m = grid.size(), n = grid[0].size();
        vector<vector<int>> dp(m + 1, vector<int>(n + 1, 0x3f3f3f3f));
        dp[1][0] = dp[0][1] = 0;
        for (int i = 1; i <= m; i++)
        {
            for (int j = 1; j <= n; j++)
            {
                dp[i][j] = min(dp[i - 1][j], dp[i][j - 1]) + grid[i - 1][j - 1];
            }
        }
        return dp[m][n];
    }
};

class Solution {
public:
    string longestPalindrome(string s) {
        int n = s.size();
        vector<vector<bool>> dp(n, vector<bool>(n));
        int begin = 0, len = 1;
        for (int i = n - 1; i >= 0; i--)
        {
            for (int j = i; j < n; j++)
            {
                if (s[i] == s[j]) dp[i][j] = i + 1 < j ? dp[i + 1][j - 1] : true;
                if (dp[i][j] && j - i + 1 > len)
                {
                    begin = i;
                    len = j - i + 1;
                }
            }
        }
        return s.substr(begin, len);
    }
};

class Solution {
public:
    int longestCommonSubsequence(string text1, string text2) {
        int m = text1.size(), n = text2.size();
        vector<vector<int>> dp(m + 1, vector<int>(n + 1));
        for (int i = 1; i <= m; i++)
        {
            for (int j = 1; j <= n; j++)
            {
                if (text1[i - 1] == text2[j - 1]) dp[i][j] = dp[i - 1][j - 1] + 1;
                else dp[i][j] = max(dp[i - 1][j], dp[i][j - 1]);
            }
        }
        return dp[m][n];
    }
};

class Solution {
public:
    int minDistance(string word1, string word2) {
        int m = word1.size(), n = word2.size();
        vector<vector<int>> dp(m + 1, vector<int>(n + 1));
        for (int i = 0; i <= m; i++) dp[i][0] = i;
        for (int i = 0; i <= n; i++) dp[0][i] = i;
        for (int i = 1; i <= m; i++)
        {
            for (int j = 1; j <= n; j++)
            {
                if (word1[i - 1] == word2[j - 1])
                    dp[i][j] = dp[i - 1][j - 1];
                else
                    dp[i][j] = min({dp[i - 1][j], dp[i][j - 1], dp[i - 1][j - 1]}) + 1;
            }
        }
        return dp[m][n];
    }
};