leetcode算法题--矩阵中严格递增的单元格数

原题链接：https://leetcode.cn/problems/maximum-strictly-increasing-cells-in-a-matrix/

优化动态规划

func maxIncreasingCells(mat [][]int) int {
    // dp[i][j] 表示从其他点到[i,j]的最长路径
    // rowMax[i] 表示第i行最大的dp[i][j]
    // colMax[j] 表示第j列最大的dp[i][j]
    // 这里将dp[i][j]优化成mx
    m, n := len(mat), len(mat[0])
    type pair struct {x, y int} 
    g := make(map[int][]pair)
    for i, row := range mat {
        for j, v := range row {
            g[v] = append(g[v], pair{i ,j})
        } 
    }

    a := make([]int, 0, len(g))
    for key := range g {
        a = append(a, key) 
    }

    sort.Ints(a)
    rowMax := make([]int, m)
    colMax := make([]int, n)
    res := 0
    for _, v := range a {
        mx := make([]int, len(g[v]))
        for i, pos := range g[v] {
            mx[i] = max(rowMax[pos.x], colMax[pos.y]) + 1
            res = max(res, mx[i]) 
        } 
        for i, pos := range g[v] {
            rowMax[pos.x] = max(rowMax[pos.x], mx[i])
            colMax[pos.y] = max(colMax[pos.y], mx[i])
        }
    } 

    return res
}

func max(a, b int) int {
    if a > b {
        return a
    }

    return b
}