62. Unique Paths

description:

https://leetcode.com/problems/unique-paths/
机器人从一堆方格的左上角走到右下角，只能往右或者往下走，问有几种走法
Note:

Example:

Example 1:Input: m = 3, n = 2
Output: 3
Explanation:
From the top-left corner, there are a total of 3 ways to reach the bottom-right corner:
1. Right -> Right -> Down
2. Right -> Down -> Right
3. Down -> Right -> RightExample 2:Input: m = 7, n = 3
Output: 28

answer:

class Solution {
public:int uniquePaths(int m, int n) {double sum = 1, up = 1;  // 这里一定是 double int mi = m < n ? m : n;  // 必须先找出最小的，虽然数学上两个排列相等，但是程序里因为数的范围限制神马的不清楚，会超时for (int i = 0; i < mi - 1; i++) {sum *= m + n - 2 - i;up *= i + 1;}return (int)(sum / up); // 最后要把double 变到 integer}
};

relative point get√：

hint :

就是在总步数 m + n - 2 里选 n-1 步（m - 1）是往下走（右）

转载于:https://www.cnblogs.com/forPrometheus-jun/p/11332791.html

62. Unique Paths相关推荐

[Leetcode]62. Unique Paths
62. Unique Paths 本题难度: Easy Topic: Dynamic Programming Description A robot is located at the top-lef ...
【动态规划】LeetCode 62. Unique Paths
LeetCode 62. Unique Paths Solution1:我的未能AC的答案递归超时了!!! class Solution { public:int uniquePaths(int m ...
Leetcode 62. Unique Paths
题目: A robot is located at the top-left corner of a m x n grid (marked 'Start' in the diagram below). ...
[LeetCode]: 62: Unique Paths
题目: A robot is located at the top-left corner of a m x n grid (marked 'Start' in the diagram below). ...
[leetcode] 62 Unique Paths (Medium)
原题链接字母题 : unique paths Ⅱ 思路: dp[i][j]保存走到第i,j格共有几种走法. 因为只能走→或者↓,所以边界条件dp[0][j]+=dp[0][j-1] 同时容易得出递推 ...
[swift] LeetCode 62. Unique Paths
A robot is located at the top-left corner of a m x n grid (marked 'Start' in the diagram below). The ...
《每日一题》62. Unique Paths 不同路径
一个机器人位于一个 m x n 网格的左上角 (起始点在下图中标记为 "Start" ). 机器人每次只能向下或者向右移动一步.机器人试图达到网格的右下角(在下图中标记为 &quo ...
[dp] LeetCode 62. Unique Paths
输入:两个int m和n 输出:一个int,表示不同路径的个数. 规则:有一个m行n列的矩阵,一个机器人从左上角走到右下角,每次向下或者向右走一格. 分析:目的是要找到从(0,0)到(m-1,n-1) ...
运用排列组合直接解62. Unique Paths
题目:https://leetcode.com/problems/unique-paths/ 典型思路是用dp来解,时间,空间均为O(n): public int uniquePaths(int m, ...