63. 不同路径 II

[rocksc30]

class Solution {
    public int uniquePathsWithObstacles(int[][] obstacleGrid) {
        int m = obstacleGrid.length;
        int n = obstacleGrid[0].length;
        if(obstacleGrid[0][0] == 1) return 0;
        if (m == 1){
            for (int i = 0; i < n; i++) {
                if (obstacleGrid[0][i] == 1) return 0;
            }
            return 1;
        }
        if (n == 1){
            for (int i = 0; i < m; i++) {
                if (obstacleGrid[i][0] == 1) return 0;
            }
            return 1;
        }
        int[][] dp = new int[m][n];
        dp[0][0] = 0;
        dp[0][1] = obstacleGrid[0][1] == 1 ? 0 : 1;
        // 初始化第一行与第一列
        for (int i = 1; i < n; i++) {
            if (obstacleGrid[0][i] == 1){
                break;
            }
            dp[0][i] = 1;
        }
        for (int i = 0; i < m; i++) {
            if (obstacleGrid[i][0] == 1){
                break;
            }
            dp[i][0] = 1;
        }
        for (int i = 1; i < m; i++) {
            for (int j = 1; j < n; j++){
                if (obstacleGrid[i][j] == 1){
                    dp[i][j] = 0;
                    continue;
                }
                dp[i][j] = dp[i - 1][j] + dp[i][j - 1];
            }
        }
        return dp[m-1][n-1];
    }
}