形成三角形的给定数组中最大的字典三元组
给定一个数组 arr[] ，任务是在该数组中找到字典上最大的可以形成三角形的三元组。如果不存在这样的三元组，打印 -1 。 例:
输入: arr[] = { 4，2，10，3，5 } 输出: 3 4 5 解释: 字典上最大的三元组是(4，5，10)。但它并不构成三角形。 下一个字典序上最大的三元组是(3，4，5)。 既然形成三角形，就是必答。 输入: arr[] = { 20，12，120，3，15 } 输出: 12 15 20
方法: 一个三元组可以形成一个三角形，当且仅当它遵循下面给出的条件:
如果 A、B、C 形成一个三元组，那么如果 T1】A<b+ C 或 B < A + C 或C<A+BT7】则三元组可以形成一个三角形
思路是用排序。按升序对数组进行排序。从数组的末尾开始遍历，检查是否有任何三元组满足上述条件。打印满足条件的第一个三元组，作为输出。如果找不到这样的三联，那么打印 -1 。 以下是上述办法的实施情况:
C++
// C++ Program to implement
// the the above approach
#include <bits/stdc++.h>
using namespace std;
// Function to find lexicographically
// largest triplet that forms a
// triangle in the given array
void findTriplet(int arr[], int N)
{
// Sort the array
sort(arr, arr + N);
int flag = 0, i;
// Iterate from the end of the array
for (i = N - 1; i - 2 >= 0; i--) {
// If the triplet forms a triangle
if (arr[i - 2] + arr[i - 1] > arr[i]) {
flag = 1;
break;
}
}
// If triplet found
if (flag) {
// Print the triplet
cout << arr[i - 2] << " "
<< arr[i - 1] << " "
<< arr[i] << endl;
}
// Otherwise
else {
cout << -1 << endl;
}
}
// Driver Code
int main()
{
int arr[] = { 4, 2, 10, 3, 5 };
int N = sizeof(arr) / sizeof(arr[0]);
findTriplet(arr, N);
return 0;
}
Java 语言(一种计算机语言，尤用于创建网站)
// Java program to implement
// the the above approach
import java.util.*;
class GFG{
// Function to find lexicographically
// largest triplet that forms a
// triangle in the given array
static void findTriplet(int arr[], int N)
{
// Sort the array
Arrays.sort(arr);
int flag = 0, i;
// Iterate from the end of the array
for(i = N - 1; i - 2 >= 0; i--)
{
// If the triplet forms a triangle
if (arr[i - 2] + arr[i - 1] > arr[i])
{
flag = 1;
break;
}
}
// If triplet found
if (flag != 0)
{
// Print the triplet
System.out.println(arr[i - 2] + " " +
arr[i - 1] + " " +
arr[i] );
}
// Otherwise
else
{
System.out.println(-1);
}
}
// Driver Code
public static void main (String []args)
{
int arr[] = { 4, 2, 10, 3, 5 };
int N = arr.length;
findTriplet(arr, N);
}
}
// This code is contributed by chitranayal
Python 3
# Python3 implementation of
# the above approach
# Function to find lexicographically
# largest triplet that forms a
# triangle in the given array
def findTriplet(arr, N):
# Sort the array
arr.sort()
# Iterate from the end of the array
i = N - 1
while i - 2 >= 0:
# If the triplet forms a triangle
if(arr[i - 2] + arr[i - 1] > arr[i]):
flag = 1
break
i -= 1
# If triplet found
if(flag):
# Print the triplet
print(arr[i - 2],
arr[i - 1],
arr[i])
# Otherwise
else:
print(-1)
# Driver Code
if __name__ == '__main__':
arr = [ 4, 2, 10, 3, 5 ]
N = len(arr)
findTriplet(arr, N)
# This code is contributed by Shivam Singh
C
// C# program to implement
// the the above approach
using System;
class GFG{
// Function to find lexicographically
// largest triplet that forms a
// triangle in the given array
static void findTriplet(int []arr, int N)
{
// Sort the array
Array.Sort(arr);
int flag = 0, i;
// Iterate from the end of the array
for(i = N - 1; i - 2 >= 0; i--)
{
// If the triplet forms a triangle
if (arr[i - 2] + arr[i - 1] > arr[i])
{
flag = 1;
break;
}
}
// If triplet found
if (flag != 0)
{
// Print the triplet
Console.Write(arr[i - 2] + " " +
arr[i - 1] + " " +
arr[i] );
}
// Otherwise
else
{
Console.Write(-1);
}
}
// Driver Code
public static void Main (string []args)
{
int []arr = { 4, 2, 10, 3, 5 };
int N = arr.Length;
findTriplet(arr, N);
}
}
// This code is contributed by Ritik Bansal
java 描述语言
<script>
// JavaScript Program to implement
// the the above approach
// Function to find lexicographically
// largest triplet that forms a
// triangle in the given array
function findTriplet(arr, N) {
// Sort the array
arr.sort((a, b) => a - b);
var flag = 0,
i;
// Iterate from the end of the array
for (i = N - 1; i - 2 >= 0; i--) {
// If the triplet forms a triangle
if (arr[i - 2] + arr[i - 1] > arr[i]) {
flag = 1;
break;
}
}
// If triplet found
if (flag) {
// Print the triplet
document.write(
arr[i - 2] +
" " +
arr[i - 1] +
" " +
arr[i] +
"<br>"
);
}
// Otherwise
else {
document.write(-1 + "<br>");
}
}
// Driver Code
var arr = [4, 2, 10, 3, 5];
var N = arr.length;
findTriplet(arr, N);
</script>
Output:
3 4 5
时间复杂度: O(Nlog(N))* 辅助空间: O(1)
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