给定一个代表三角形图案最后一项的数字N。任务是从1到N打印三角形图案,以使每一行都是完整的。
三角形图案的给出方式为:
1
2 3
4 5 6
7 8 9 10
.
.
例子:
Input: N = 3
Output:
1
2 3
Input: N = 7
Output:
1
2 3
4 5 6
7 will not be printed as
it would result in an incomplete row
方法:
- 从给定的最后一项N中找到完整的行数。
- 作为:
对于最大高度= 1,最后一项将是1
对于最大高度= 2,最后一项将是3
对于最大高度= 3,最后一项将是6 - 所以最后一项形成了一个模式:1、3、6、10、15…
- 因此,系列1、3、6、10、15,…的第n个项
A(n)= 1 + 2 + 3 + 4…+(n – 1)+ n
= n(n + 1)/ 2
即A(n)是前n个自然数的总和。 - 所以在
- 作为:
A(n) = n(n + 1) / 2
A(n) represents the last term (as per our problem),
and n represents the max height of the Triangle
- 因此,可以将其视为:
Last term = height (height + 1) / 2
- 所以,
height = (-1 + sqrt(1 + 8*lastTerm)) / 2
- 找到最大高度后,可以轻松打印三角形图案。
下面是上述方法的实现:
C++
// C++ code for printing the
// Triangle Pattern using last term N
#include
using namespace std;
// Function to demonstrate printing pattern
void triangle(int n)
{
// number of spaces
int k = 2 * n - 2;
// character to be printed
int ch = 1;
// outer loop to handle number of rows
// n in this case
for (int i = 0; i < n; i++) {
// inner loop to handle number spaces
// values changing acc. to requirement
for (int j = 0; j < k; j++)
cout << " ";
// decrementing k after each loop
k = k - 1;
// inner loop to handle number of columns
// values changing acc. to outer loop
for (int j = 0; j <= i; j++) {
// printing stars
cout << ch++ << " ";
}
// ending line after each row
cout << endl;
}
}
// Function to find the max height
// or the number of lines
// in the triangle pattern
int maxHeight(int n)
{
return (((int)sqrt(1 + 8.0 * n)) - 1) / 2;
}
// Driver Function
int main()
{
int N = 9;
triangle(maxHeight(N));
return 0;
}
Java
// Java code for printing the
// Triangle Pattern using last term N
import java.util.*;
class GFG
{
// Function to demonstrate printing pattern
static void triangle(int n)
{
// number of spaces
int k = 2 * n - 2;
// character to be printed
int ch = 1;
// outer loop to handle number of rows
// n in this case
for (int i = 0; i < n; i++)
{
// inner loop to handle number spaces
// values changing acc. to requirement
for (int j = 0; j < k; j++)
System.out.print(" ");
// decrementing k after each loop
k = k - 1;
// inner loop to handle number of columns
// values changing acc. to outer loop
for (int j = 0; j <= i; j++)
{
// printing stars
System.out.print(ch++ + " ");
}
// ending line after each row
System.out.println();
}
}
// Function to find the max height
// or the number of lines
// in the triangle pattern
static int maxHeight(int n)
{
return (((int)Math.sqrt(1 + 8.0 * n)) - 1) / 2;
}
// Driver Code
public static void main(String[] args)
{
int N = 9;
triangle(maxHeight(N));
}
}
// This code is contributed by PrinciRaj1992
Python3
# Python3 code for printing the
# Triangle Pattern using last term N
from math import sqrt
# Function to demonstrate printing pattern
def triangle(n) :
# number of spaces
k = 2 * n - 2;
# character to be printed
ch = 1;
# outer loop to handle number of rows
# n in this case
for i in range(n) :
# inner loop to handle number spaces
# values changing acc. to requirement
for j in range(k) :
print(" ", end = "");
# decrementing k after each loop
k = k - 1;
# inner loop to handle number of columns
# values changing acc. to outer loop
for j in range(i + 1) :
# printing stars
print(ch, end = " ");
ch += 1;
# ending line after each row
print()
# Function to find the max height
# or the number of lines
# in the triangle pattern
def maxHeight(n) :
ans = (sqrt(1 + 8.0 * n) - 1) // 2;
return int(ans);
# Driver Code
if __name__ == "__main__" :
N = 9;
triangle(maxHeight(N));
# This code is contributed by AnkitRai01
C#
// C# code for printing the
// Triangle Pattern using last term N
using System;
class GFG
{
// Function to demonstrate printing pattern
static void triangle(int n)
{
// number of spaces
int k = 2 * n - 2;
// character to be printed
int ch = 1;
// outer loop to handle number of rows
// n in this case
for (int i = 0; i < n; i++)
{
// inner loop to handle number spaces
// values changing acc. to requirement
for (int j = 0; j < k; j++)
Console.Write(" ");
// decrementing k after each loop
k = k - 1;
// inner loop to handle number of columns
// values changing acc. to outer loop
for (int j = 0; j <= i; j++)
{
// printing stars
Console.Write(ch++ + " ");
}
// ending line after each row
Console.WriteLine();
}
}
// Function to find the max height
// or the number of lines
// in the triangle pattern
static int maxHeight(int n)
{
return (((int)Math.Sqrt(1 + 8.0 * n)) - 1) / 2;
}
// Driver Code
public static void Main(String[] args)
{
int N = 9;
triangle(maxHeight(N));
}
}
// This code is contributed by Princi Singh
Javascript
输出:
1
2 3
4 5 6