leetcode Triangle

题目连接

https://leetcode.com/problems/triangle/  

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;
	}
};