标签：style class blog code ext color
Decription:
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).
Note:
Bonus point if you are able to do this using only O(n) extra space, where n is the total number of rows in the triangle.
分析：这丫就是一个动态规划题，根据上一层各个元素的最小和来计算下一层各个元素的和。 因为要用O(n)的空间解决，n是三角形行数
，其实就是最长一行的元素个数，这个空间主要是用来记录上一行各个元素和的最小值，要保证只用这一个数组，则需要将这一行元素从后
往前处理，保证新产生的和值，不会覆盖到上一行。
#define INF 0x3f3f3f3f class Solution { public: int minimumTotal(vector<vector<int> > &triangle) { int rownum = triangle.size(); if(rownum==0) return 0; int *pathrec = new int[rownum]; memset(pathrec,0,sizeof(pathrec)); pathrec[0] = triangle[0][0]; for(int i=1;i<rownum;i++) { int elenum = triangle[i].size(); for(int j=elenum-1;j>=0;--j) { int minval = INF; if(j<triangle[i-1].size()) minval = min(minval,pathrec[j]+triangle[i][j]); if(j-1>=0) minval = min(minval,pathrec[j-1]+triangle[i][j]); pathrec[j] = minval; } } int minval = INF; for(int i=0;i<rownum;i++) minval = min(minval,pathrec[i]); return minval; } };
Leetcode:Triangle,布布扣,bubuko.com
标签：style class blog code ext color
原文地址：http://www.cnblogs.com/soyscut/p/3787542.html
