zoukankan      html  css  js  c++  java
  • 931. Minimum Falling Path Sum

    package LeetCode_931
    
    /**
     * 931. Minimum Falling Path Sum
     * https://leetcode.com/problems/minimum-falling-path-sum/
     *
     * Given a square array of integers A, we want the minimum sum of a falling path through A.
    A falling path starts at any element in the first row, and chooses one element from each row.
    The next row's choice must be in a column that is different from the previous row's column by at most one.
    
    Example 1:
    Input:
    [
    [1,2,3],
    [4,5,6],
    [7,8,9]
    ]
    Output: 12
    Explanation:
    The possible falling paths are:
    [1,4,7], [1,4,8], [1,5,7], [1,5,8], [1,5,9]
    [2,4,7], [2,4,8], [2,5,7], [2,5,8], [2,5,9], [2,6,8], [2,6,9]
    [3,5,7], [3,5,8], [3,5,9], [3,6,8], [3,6,9]
    The falling path with the smallest sum is [1,4,7], so the answer is 12.
    
    Constraints:
    1. 1 <= A.length == A[0].length <= 100
    2. -100 <= A[i][j] <= 100
     * */
    class Solution {
        /*
        * solution : DP, Bottom-Up, for example array is:
        * [
            [1,2,3],
            [4,5,6],
            [7,8,9]
            ]
           fill new value from second row, the value of current i,j is: current value + min(A[i-1][j], A[i-1][j+1])
            [1,2,3],
            [5,6,8],//<-this row after fill by: 4+min(1,2), 5+min(1,min(2,3)), 6+min(2,3)
            [12,13,15],//<-this row after fill by: 7+min(5,6), 8+min(5,min(6,8)), 9+min(6,8)
            result is minimum in last row
    
            Time complexity:O(nn), Space complexity:O(1)
        * */
        fun minFallingPathSum(A: Array<IntArray>): Int {
            if (A == null || A.isEmpty()) {
                return 0
            }
            val n = A.size
            if (n == 1) {
                return A[0][0]
            }
            for (i in 1 until n) {//start from second row
                for (j in 0 until n) {
                    if (j == 0) {
                        A[i][j] += Math.min(A[i - 1][j], A[i - 1][j + 1])
                    } else if (j == n - 1) {
                        A[i][j] += Math.min(A[i - 1][j - 1], A[i - 1][j])
                    } else {
                        A[i][j] += Math.min(A[i - 1][j - 1], Math.min(A[i - 1][j + 1], A[i - 1][j]))
                    }
                }
            }
            var result = Int.MAX_VALUE
            for (cols in 0 until n) {
                result = Math.min(result, A[n - 1][cols])
            }
            return result
        }
    }
  • 相关阅读:
    Mac保留Python2安装Python3(Anaconda3)
    Mybatis Plugin 以及Druid Filer 改写SQL
    Jackson替换fastjson
    Java单元测试 Http Server Mock框架选型
    应用中有多个Spring Property PlaceHolder导致@Value只能获取到默认值
    RabbitMQ Policy的使用
    Collectors.toMap不允许Null Value导致NPE
    php 删除标签
    php 替换标签
    jquery拼接html
  • 原文地址:https://www.cnblogs.com/johnnyzhao/p/14006436.html
Copyright © 2011-2022 走看看