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UniquePathsII.java
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58 lines (55 loc) · 1.88 KB
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package com.yangchd.leetcode.medium;
/**
* @author yangchd 2018/10/21
*
* 63.Unique Paths II
* A robot is located at the top-left corner of a m x n grid (marked 'Start' in the diagram below).
* The robot can only move either down or right at any point in time. The robot is trying to reach the bottom-right corner of the grid (marked 'Finish' in the diagram below).
* Now consider if some obstacles are added to the grids. How many unique paths would there be?
*
* Note: m and n will be at most 100.
*
* Example 1:
* Input:
* [
* [0,0,0],
* [0,1,0],
* [0,0,0]
* ]
* Output: 2
* Explanation:
* There is one obstacle in the middle of the 3x3 grid above.
* There are two ways to reach the bottom-right corner:
* 1. Right -> Right -> Down -> Down
* 2. Down -> Down -> Right -> Right
*
*/
public class UniquePathsII {
/**
* 后一步的可能是左上两部分相加
*/
public class Solution {
public int uniquePathsWithObstacles(int[][] obstacleGrid) {
int m = obstacleGrid.length;
int n = obstacleGrid[0].length;
for (int r = 0; r < m; r++) {
for (int c = 0; c < n; c++) {
if (obstacleGrid[r][c] == 1) {
obstacleGrid[r][c] = 0;
} else {
if (r == 0 && c == 0) {
obstacleGrid[r][c] = 1;
} else if (r == 0) {
obstacleGrid[r][c] = obstacleGrid[r][c - 1];
} else if (c == 0) {
obstacleGrid[r][c] = obstacleGrid[r - 1][c];
} else {
obstacleGrid[r][c] = obstacleGrid[r][c - 1] + obstacleGrid[r - 1][c];
}
}
}
}
return obstacleGrid[m - 1][n - 1];
}
}
}