LeetCode 063、不同路径 II

LeetCode 063、

题目

题解

五部曲分析问题，注意递推公式：

dp[i][j] = dp[i - 1][j] + dp[i][j - 1]; (i, j)如果是障碍的话就应该保持初始状态0

class Solution {
          
   
public:
    int uniquePathsWithObstacles(vector<vector<int>>& obstacleGrid) {
          
   
        int row = obstacleGrid.size();
        int col = obstacleGrid[0].size();
        vector<vector<int>> dp(row, vector<int>(col, 0));
        for (int i = 0; i < row && obstacleGrid[i][0] == 0; ++i) dp[i][0] = 1;
        for (int j = 0; j < col && obstacleGrid[0][j] == 0; ++j) dp[0][j] = 1;
        for (int i = 1; i < row; ++i) {
          
        // 注意i从1开始
            for (int j = 1; j < col; ++j) {
          
    // 同样注意，j从1开始
                if (obstacleGrid[i][j] == 0) {
          
   
                    dp[i][j] = dp[i - 1][j] + dp[i][j - 1];
                }
            }
        }
        return dp[row - 1][col - 1];
    }
};