【leetcode】Triangle

Question：

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]]

Anwser 1：      

class Solution {public:    int minimumTotal(vector<vector<int> > &triangle) {        // Start typing your C/C++ solution below        // DO NOT write int main() function        int rows = triangle.size();        if(0 == rows) return 0;                int *minSums = new int[rows];        int *temp = new int[rows];                for(int r = 0; r < rows; r++) {            vector<int> vec = triangle[r];            temp[0] = vec[0] + (r > 0 ? minSums[0] : 0);            for(int i = 1; i < r; i++) {                temp[i] = vec[i] + min(minSums[i-1], minSums[i]);            }                        if(r > 0) {                temp[r] = vec[r] + minSums[r-1];            }                            int *tswap = temp;            temp = minSums;            minSums = tswap;        }                int m = minSums[0];        for(int i = 1; i < rows; i++)         {            if(minSums[i] < m){                m = minSums[i];            }         }                delete temp;        delete minSums;        return m;    }};

Anwser 2：     

class Solution {public:    int minimumTotal(vector<vector<int> > &triangle) {        // Start typing your C/C++ solution below        // DO NOT write int main() function        int line = triangle.size();        for(int i = line -2 ; i >= 0; i--)         {            for(int j = 0; j < triangle[i].size(); j++)            {                triangle[i][j] += min(triangle[i+1][j], triangle[i+1][j+1]);            }        }        return triangle[0][0];    }};

Anwser 3：

class Solution {public:        void run(vector<vector<int> > &triangle, int row, int idx, int curSum, int &minPath)    {        if (row == triangle.size())        {            minPath = min(minPath, curSum);            return;        }                run(triangle, row + 1, idx, curSum + triangle[row][idx], minPath);        run(triangle, row + 1, idx + 1, curSum + triangle[row][idx], minPath);    }    int minimumTotal(vector<vector<int> > &triangle) {        // Start typing your C/C++ solution below        // DO NOT write int main() function        int minPath = INT_MAX;                if (triangle.size() == 0) {            return 0;        }                run(triangle, 0, 0, 0, minPath);                return minPath;    }};

注意點：

1） Judge Small is ok， but Judge Large is error

2） 如果迭代很深的話，容易造成壓棧佔用記憶體很高，超出段後會溢出