White entry input pyramid pattern, the number of input control lines. (Nested loops)

#include<stdio.h>
void main()
{
    int i,j,n;
    printf("Please input n:\n");
    scanf("%d",&n);
    if(n<0)
        printf("行数错误！\n");
    else
    {
        for(j=1;j<=n;j++)
        {
            for(i=1;i<=j;i++)
            {
                printf("*");
            }
            printf("\n");
        }
    }
} 

There are two control cycle count variable i, j.

To find the relationship between the j, the relationship between two variables control loop and i,.

Example: Pyramid *

　　　　　　　***

　　　　　　　*****

　　　　　　　******* * two line increases, the number of control lines and the variable j, i and the number of control variables for each line,

　　　　　　　　　　Relationship  I * = J-2. 1   . Therefore, the inner loop control condition for (i = 1; i < = 2 * j-1; i ++)

if(n<0)
        printf("Input error!");
    else
    {
        for(j=1;j<=n;j++)
        {
            for(i=1;i<=2*j-1;i++)
            {
                printf("*");
            }
            printf("\n");
        }
    }

 Another example: inverted triangle *******

　　　　　　　  *****

　　　　　　　  ***

　　　　　　      * Controls the relationship between the number j, and the number of I,   2 * + n-1-2 * J     (n-number of input lines of the pyramid)