杨辉三角输出

Ss 杨辉三角标准输出tips：（先提供思路，读者自己先试着完成）

       1以行数约定输出的数目

     2根据行数计算出可能出现的最大的字宽，而且每次输出的空格数目等于最大的字宽宽度，每个数字都要以同样的字宽输出，printf(“%3d”);

       3编写组合数计算公式combi(int row, int col)

       4当前要输出的数字根据其行列有combi计算出来，即C(row,col)

       5每行输出的内容是先空格，再数字，行尾输出换行

       6组合数的计算：利用迭代计算，C(N,K)àC(N,K+1); 起始C(N,0)=1;

接下来提供答案：

#include 
#include
#define N 15
long combi(int n, int r){                              //function to compute combinatorial numbers
	int i;
	long p = 1;
	for (i = 1; i <= r; i++)
		p = p * (n - i + 1) / i;
	return p;
}
void main(int argv,char**argc) {
	int n, r, t;
	for (n = 0; n <= N; n++) {											//there are N+1 rows in total
		for (r = 0; r <= n; r++) {                                      // there are n+1 numbers in number n row 
			int i;                                   //the sequence of print is space first and then numbers
			if (r == 0) {				//print the spaces before the first number in every row
				for (i = 0; i <= (N - n); i++)
					printf("    ");    //3 spaces is according to the width of longest numbers and every number should set the same width
			}
			else {                       //print space among numbers
				printf("    ");
			} 
			printf("%4d", combi(n, r));    //print numbers  combi is used to compute combinatorial numbers according to its row and col.
		}
		printf("\n");                        //line break/line feed
	}
	system("pause");
}