LintCode: Triangle

C++

逆推

 class Solution {
 public:
     /**
      * @param triangle: a list of lists of integers.
      * @return: An integer, minimum path sum.
      */
     int minimumTotal(vector<vector<int> > &triangle) {
         // write your code here
         if (triangle.size() == )
             return ;

         vector<int> dp(triangle.size());

         dp[] = triangle[][];
         for(int i = ; i < triangle.size(); i++)
             for(int j = triangle[i].size() - ; j >= ; j--)
                 if (j == )
                     dp[j] = dp[j] + triangle[i][j];
                 else if (j == triangle[i].size() - )
                     dp[j] = dp[j-] + triangle[i][j];
                 else
                     dp[j] = min(dp[j-], dp[j]) + triangle[i][j];

         int ret = INT_MAX;
         for(int i = ; i < dp.size(); i++)
             ret = min(ret, dp[i]);

         return ret;
     }
 };

C++,修改原数组

 class Solution {
 public:
     /**
      * @param triangle: a list of lists of integers.
      * @return: An integer, minimum path sum.
      */
     int minimumTotal(vector<vector<int> > &triangle) {
         // write your code here
         for (int i = triangle.size() - ; i >= ; --i){
           for (int j = ; j < i + ; ++j){
             if(triangle[i+][j] > triangle[i+][j+]){
               triangle[i][j] += triangle[i+][j+];
             }else{
               triangle[i][j] += triangle[i+][j];
             }
           }
         }
         return triangle[][];
     }
 };