C + + Print triangles

Requires the use of the C + + language to print as a shape under a console project.

　　　　

This is a different number of * symbols, different numbers of space characters, line breaks arranged in the 8-column horizontal lines, according to the regular arrangement of a positive triangle.

① first analyzes what we need to print:

1. In addition to the last line (line eighth), there are a number of whitespace characters before the * symbol of the first line to the seventh line that makes up the triangle.
2. The * symbol that makes up the triangle.
3. A newline character between each row and the next line.

② Consider the number of prints per line (whitespace, * symbol, line break):

1. The first is the space character, according to the graphical observation can get the relationship between the number of spaces and line number:

Current line number The number of characters in the current line

1 7

2 6

3 5

4 4

5 3

6 2

....　　　　　　　 ....

This concludes the formula: number of current spaces = Maximum line number-current line number

2. Next is the number of * symbols, as well as the number of symbols and line numbers can be obtained by observing the graphs:

Current line number Current line * character number

1 1

2 3

3 5

4 7

5 9

6 11

This concludes the formula: Current * Number = Current line number * 2-1

3, the last is a newline character, it is obvious that in addition to the last line of each of the remaining lines only need a newline character to print out the current line of space and * characters after the line.

③ finally we consider what idioms can be finished printing:

There are three types of loop structures in C + +, do and for, where the number of content to print is determined, so we prefer to use a for loop to accomplish this task.

The number of space characters, * symbols, and line breaks required to print above requires line numbers to participate in the calculation.

We declare an int type variable i to represent the current line number, using I to replace the above formula:

I line number of spaces = Maximum line number-I

I line * Number of characters = i * 2-1

I line break number: 1

Get the following code:

int i,j,k;

for (i = 1; I <= 8; i++) {//The control row determines the current line number at the time of the loop, and in turn corresponds to the 1~8 row of the triangle.
for (j = 1; J <= 8-i; j + +) {//The control line determines the number of characters to print, and I determines the line number.
printf ("");
}
for (k = 1; K <= i*2-1; k++) {//The control line determines the number of print * symbols, and I determines the line number.
printf ("*");
}
printf ("\ n"); Print a newline character per line.
}

The final code is not the key, and you should focus on the analysis process when you see the problem.

C + + Print triangles