LeetCode OJ--Triangle **

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

一个三角形，类似于杨辉三角的形状，求从上到下最小的路径和，但走每一步都得是相邻的。

动态规划，从下到上一层层来。

sum[i] = min{sum[i]+triangle[i][j],sum[i+1]+triangle[i][j]}

有一个保存每一个点数值的过程。

#include <iostream>
#include <vector>
using namespace std;

class Solution {
public:
    int minimumTotal(vector<vector<int> > &triangle) {
        int row = triangle.size();
        if(row == 0)
            return 0;
        if(row == 1)
            return triangle[0][0];

        //initialize
        vector<int> sum;
        sum.resize(row);
        for(int i = 0;i<triangle[row-1].size();i++)
            sum[i] = triangle[row-1][i];

        for(int i = row-2;i>=0;i--)
        {
            for(int j = 0;j<=i;j++)
            {
                int min1 = sum[j]<sum[j+1]?sum[j]:sum[j+1];
                sum[j] = min1 + triangle[i][j];
            }
        }
        return sum[0];
    }
};

int main()
{
    class Solution myS;
    vector<int> v1;
    v1.push_back(-1);
    vector<int> v2;
    v2.push_back(-2);
    v2.push_back(-3);
    vector<int> v3;
    v3.push_back(6);
    v3.push_back(5);
    v3.push_back(7);
    vector<int> v4;
    v4.push_back(4);
    v4.push_back(1);
    v4.push_back(8);
    v4.push_back(3);

    vector<vector<int> > num;
    num.push_back(v1);
    num.push_back(v2);
    num.push_back(v3);
    num.push_back(v4);
    cout<<myS.minimumTotal(num);
 
    return 0;
}