杨辉三角(三角形)

		int a = 0;
	    int arr[][] = new int[3][5];
	    int top,top_left = 0,top_right = 0;
	    for(; a < 3; a++){
	        int b = 0;
	        for(;b < 5; b++){
	            top = a - 1;
	            top_left = b - 1;
	            top_right = b + 1;
	            if(a==0){
	            	int temp = 5>>1;
	        		if(temp==b){
	        			arr[a][b] = 1;
	        		}else{
	        			arr[a][b] = 0;
	        		}
		            System.out.print(arr[a][b]+",");
	            }else if(a==3-1){
	            	if(b==0||b==5-1){
		            	arr[a][b] = 1;
		            	System.out.print(arr[a][b]+",");
		            }else{
		            	if(top<0||top_right>=5||top_left<0){
		            		arr[a][b] = 0;
		            		System.out.print(arr[a][b]+",");
			            }else{
			            	arr[a][b] = arr[top][top_left] + arr[top][top_right];
				            System.out.print(arr[a][b]+",");
			            }
		            }
	            }else{
	            	if(top<0||top_right>=5||top_left<0){
	            		arr[a][b] = 0;
	            		System.out.print(arr[a][b]+",");
		            }else{
		            	arr[a][b] = arr[top][top_left] + arr[top][top_right];
			            System.out.print(arr[a][b]+",");
		            }
	            }          
	        }
	        System.out.println();
	    }