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120. Triangle
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.
参考资料
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/**
* Runtime: 1 ms, faster than 99.42% of Java online submissions for Triangle.
* Memory Usage: 39.2 MB, less than 8.16% of Java online submissions for Triangle.
*/
public int minimumTotal(List<List<Integer>> triangle) {
int[] sums = new int[triangle.size() + 1];
for (int i = triangle.size() - 1; i >= 0; i--) {
List<Integer> row = triangle.get(i);
for (int j = 0; j < row.size(); j++) {
sums[j] = Math.min(sums[j], sums[j + 1]) + row.get(j);
}
}
return sums[0];
}