題目
鏈接:https://leetcode.com/problems/largest-perimeter-triangle/
Given an array A of positive lengths, return the largest perimeter of a triangle with non-zero area, formed from 3 of these lengths.
If it is impossible to form any triangle of non-zero area, return 0.
Example 1:
Input: [2,1,2]
Output: 5
Example 2:
Input: [1,2,1]
Output: 0
Example 3:
Input: [3,2,3,4]
Output: 10
Example 4:
Input: [3,6,2,3]
Output: 8
Note:
3 <= A.length <= 10000
1 <= A[i] <= 10^6
思路
一個面積不爲空的三角形,那麼必須要最小的兩條邊之和大於第三邊,才能構成一個三角形。並且要周長最大。很容易想到,先對數據進行排序,從最大的開始進行篩選,像窗口一樣,往左側移動,一旦找到符合條件的三角形,就是面積最大的。
public int largestPerimeter(int[] A) {
Arrays.sort(A);
for (int i = A.length - 3; i >= 0; i--) {
if (A[i] + A[i + 1] > A[i + 2]) {
return A[i] + A[i + 1] + A[i + 2];
}
}
return 0;
}