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70 lines
1.7 KiB
Markdown
70 lines
1.7 KiB
Markdown
# [812. Largest Triangle Area](https://leetcode.com/problems/largest-triangle-area/)
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## 题目
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You have a list of points in the plane. Return the area of the largest triangle that can be formed by any 3 of the points.
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```
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Example:
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Input: points = [[0,0],[0,1],[1,0],[0,2],[2,0]]
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Output: 2
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Explanation:
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The five points are show in the figure below. The red triangle is the largest.
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```
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**Notes**:
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- `3 <= points.length <= 50`.
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- No points will be duplicated.
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- `-50 <= points[i][j] <= 50`.
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- Answers within `10^-6` of the true value will be accepted as correct.
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## 题目大意
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给定包含多个点的集合，从其中取三个点组成三角形，返回能组成的最大三角形的面积。
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## 解题思路
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- 给出一组点的坐标，要求找出能组成三角形面积最大的点集合，输出这个最大面积。
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- 数学题。按照数学定义，分别计算这些能构成三角形的点形成的三角形面积，最终输出最大面积即可。
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## 代码
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```go
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package leetcode
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func largestTriangleArea(points [][]int) float64 {
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maxArea, n := 0.0, len(points)
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for i := 0; i < n; i++ {
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for j := i + 1; j < n; j++ {
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for k := j + 1; k < n; k++ {
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maxArea = max(maxArea, area(points[i], points[j], points[k]))
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}
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}
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}
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return maxArea
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}
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func area(p1, p2, p3 []int) float64 {
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return abs(p1[0]*p2[1]+p2[0]*p3[1]+p3[0]*p1[1]-p1[0]*p3[1]-p2[0]*p1[1]-p3[0]*p2[1]) / 2
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}
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func abs(num int) float64 {
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if num < 0 {
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num = -num
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}
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return float64(num)
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}
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func max(a, b float64) float64 {
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if a > b {
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return a
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}
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return b
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}
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``` |