代码随想录算法训练营第三十四天 | 动态规划 part02

62.不同路径

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

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

63. 不同路径 II

class Solution {
public:
    int uniquePathsWithObstacles(vector<vector<int>>& obstacleGrid) {
        int m = obstacleGrid.size();
        int n = obstacleGrid[0].size();
        vector<vector<int>> dp(m, vector<int>(n, 0));
        for (int i = 0; i < n; ++i) {
            if (obstacleGrid[0][i] != 1) {
                dp[0][i] = 1;
            }
            else 
                break;
        }
        for (int i = 0; i < m; ++i) {
            if (obstacleGrid[i][0] != 1) {
                dp[i][0] = 1;
            }
            else 
                break;
        }
        for (int i = 1; i < m; ++i) {
            for (int j = 1; j < n; ++j) {
                if (obstacleGrid[i][j] == 1)
                    dp[i][j] = 0;
                else
                    dp[i][j] = dp[i][j - 1] + dp[i - 1][j];
            }
        }
        
        return dp[m - 1][n - 1];
    }
};