[LintCode/LeetCode] Unique Paths

Gu_Yan 發布于2019-08-14 15:27 / 2768人閱讀

摘要：簡單的動規題目，建立數組。坐標為矩陣的坐標，值為從左上角到這一格的走法總數。賦初值，最上一行和最左列的所有格子的走法都只有一種，其余格子的走法等于其左邊格子走法與上方格子走法之和。最后，返回即可。

Problem

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).

How many possible unique paths are there?

Note

簡單的動規題目，建立dp數組。dp[i][j]坐標為矩陣的坐標，值為從左上角到這一格的走法總數。賦初值，最上一行和最左列的所有格子的走法都只有一種，其余格子的走法等于其左邊格子走法與上方格子走法之和。最后，返回dp[m-1][n-1]即可。

Solution

二維DP

public class Solution {
    public int uniquePaths(int m, int n) {
        int[][] dp = new int[m][n];
        for (int i = 0; i < m; i++) {
            for (int j = 0; j < n; j++) {
                if (i == 0 || j == 0) dp[i][j] = 1;
                else dp[i][j] = dp[i-1][j] + dp[i][j-1];
            }
        }
        return dp[m-1][n-1];
    }
}

一維DP

public class Solution {
    public int uniquePaths(int m, int n) {
        int[] dp = new int[n];
        Arrays.fill(dp, 1);
        for (int i = 1; i < m; i++) {
            for (int j = 1; j < n; j++) {
                dp[j] += dp[j-1];
            }
        }
        return dp[n-1];
    }
}

云服務器 GPU云服務器 Paths unique Mysql_unique array_unique

文章版權歸作者所有，未經允許請勿轉載,若此文章存在違規行為，您可以聯系管理員刪除。

轉載請注明本文地址：http://specialneedsforspecialkids.com/yun/65769.html

[LintCode/LeetCode] Unique Paths II

摘要：和完全一樣的做法，只要在初始化首行和首列遇到時置零且即可。對了，數組其它元素遇到也要置零喏，不過就不要啦。 Problem Follow up for Unique Paths: Now consider if some obstacles are added to the grids. How many unique paths would there be? An obstacle...

firim 2019-08-14 15:29 評論0 收藏0
[LintCode/LeetCode] First Unique Character in a S

Problem Given a string, find the first non-repeating character in it and return its index. If it doesnt exist, return -1. Example Given s = lintcode, return 0. Given s = lovelintcode, return 2. Tags A...

Xufc 2019-08-15 13:27 評論0 收藏0
[LintCode/LeetCode] Combination Sum I & II

摘要：和唯一的不同是組合中不能存在重復的元素，因此，在遞歸時將初始位即可。 Combination Sum I Problem Given a set of candidate numbers (C) and a target number (T), find all unique combinations in C where the candidate numbers sums to T...

ThreeWords 2019-08-14 15:23 評論0 收藏0
[LintCode/LeetCode] Minimum Window Substring

Problem Given a string source and a string target, find the minimum window in source which will contain all the characters in target. Notice If there is no such window in source that covers all charac...

Corwien 2019-08-14 15:43 評論0 收藏0
[LintCode/LeetCode] 3Sum

摘要：雙指針法的解法。然后用和夾逼找到使三數和為零的三數數列，放入結果數組。對于這三個數，如果循環的下一個數值和當前數值相等，就跳過以避免中有相同的解。 Problem Given an array S of n integers, are there elements a, b, c in S such that a + b + c = 0? Find all unique triplet...

Sunxb 2019-08-14 15:42 評論0 收藏0