leetcode Triangle

原題鏈接：https://leetcode.com/problems/triangle/

Description

Given a triangle, find the minimum path sum from top to bottom. Each step you may move to adjacent numbers on the row below.

For example, given the following triangle
[
[2],
[3,4],
[6,5,7],
[4,1,8,3]
]
The minimum path sum from top to bottom is 11 (i.e., 2 + 3 + 5 + 1 = 11).

class Solution {
public:
    int minimumTotal(vector<vector<int>>& triangle) {
        if (triangle.empty() || triangle[0].empty()) return 0;
        n = triangle.size();
        arr = triangle;
        dp.resize(n, vector<int>(n));
        return dfs(0, 0);
    }
private:
    int n;
    vector<vector<int>> dp;
    vector<vector<int>> arr;
    int dfs(int i, int j) {
        int ret;
        if (i >= n || j >= n) return 0;
        if (dp[i][j]) return dp[i][j];
        if (i == n - 1) ret = 0;
        ret = arr[i][j] + min(dfs(i + 1, j), dfs(i + 1, j + 1));
        return dp[i][j] = ret;
    }
};