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Yang Hui's triangle is composed of positive integers, and the numbers are symmetrical. Each row starts from 1 and gradually becomes larger, then becomes smaller, and returns to 1; each number in Yang Hui's triangle is its upper left We can understand it as the sum of the square and the number in the upper right corner as a two-dimensional array, which outputs the data through two loops.
1. What is Yang Hui Triangle?
Yang Hui triangle is a way of writing binomial coefficients. Because the arrangement shape is similar to a triangle, it is called Yang Hui triangle.
Yang Hui’s triangle is composed of positive integers, and the numbers are symmetrical. Each row starts from 1 and gradually becomes larger, then becomes smaller, and returns to 1; each number in Yang Hui’s triangle is the sum of the numbers in its upper left and upper right. We can understand it as a two-dimensional array and output the data through two loops.
2. How to use PHP to achieve it?
We can create a new array to store the array elements output through the loop, customize a function to implement this function, and finally implement it by calling the function.
<?php function triangle($n){ $arr = array(); //使用嵌套的for循环来输出二维数组元素 for($i = 1;$i <= $n;$i++){ for($j = 1;$j <= $i;$j++){ if($i == 1 || $i == $j){ //循环打印前两行 echo $arr[$i][$j] = 1; }else{ //循环打印后面的行 echo $arr[$i][$j] = $arr[$i-1][$j-1] + $arr[$i-1][$j]; } echo " "; } echo "<br/>"; } /通过调用自定义函数来打印10行的杨辉三角 triangle(10); ?>
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