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index.js
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/*
* @lc app=leetcode id=63 lang=javascript
*
* [63] Unique Paths II
*
* https://leetcode.com/problems/unique-paths-ii/description/
*
* algorithms
* Medium (33.22%)
* Total Accepted: 254.5K
* Total Submissions: 750.7K
* Testcase Example: '[[0,0,0],[0,1,0],[0,0,0]]'
*
* 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?
*
*
*
* An obstacle and empty space is marked as 1 and 0 respectively in the grid.
*
* 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
*
*
*/
/**
* @param {number[][]} obstacleGrid
* @return {number}
*/
var uniquePathsWithObstacles = function(obstacleGrid) {
if (obstacleGrid[0][0]) {
return 0;
}
const dp = [];
obstacleGrid.forEach((row, index) => {
if (index === 0) {
dp[index] = [1]
return;
}
if (row[0] || dp[index - 1][0] === 0) {
dp[index] = [0];
return;
}
dp[index] = [1];
});
obstacleGrid[0].forEach((item, index) => {
if (index === 0) {
return;
}
if (item === 1 || dp[0][index - 1] === 0) {
dp[0][index] = 0;
return;
}
dp[0][index] = 1;
});
for (let i = 1; i < obstacleGrid.length; i++) {
for (let j = 1; j < obstacleGrid[i].length; j++) {
if (obstacleGrid[i][j] === 1) {
dp[i][j] = 0;
} else {
dp[i][j] = dp[i - 1][j] + dp[i][j - 1];
}
}
}
return dp.pop().pop();
};
console.log(uniquePathsWithObstacles([[0,0],[1,1],[0,0]]))
module.exports = {
id:'63',
title:'Unique Paths II',
url:'https://leetcode.com/problems/unique-paths-ii/description/',
difficulty:'Medium',
}