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.
解:为了实现O(n),只开一个一元数组,遍历每一层时可替换数组中的值
代码:
class Solution {
public:
int minimumTotal(vector<vector<int> >& triangle) {
int size = triangle.size();
vector<int> dp(size);
for (int i = 0; i < size; i++) dp[i] = triangle[size-1][i];
for (int j = size-2; j >= 0; j--) {
for (int i = 0; i <= j; i++) {
dp[i] = triangle[j][i] + min(dp[i], dp[i+1]);
}
}
return dp[0];
}
};