问题
so I'm very new to C and am wondering how I could create the following spiral shape:
This is my comical attempt..
#include <stdio.h>
int main(void) {
int size;
int i,j;
printf("Enter size: ");
scanf("%d", &size);
for (i = 0, j = 0; i < size - 4; i++, j+=2) {
int row = 1;
while (row <= size) {
int column = 1;
while (column <= size) {
if ((row == 1 + j && column > j && column < size - j)||
(row == size - (j) && column > j && column < size - j) ||
(column == size - (j) && row > j && row <= size - j) ||
(column == 1 + j && row > (2+j) && row < size - j)) {
printf("*");
}
else {
printf("-");
}
column++;
}
row++;
printf("\n");
}
}
return 0;
}
Any help would be greatly appreciated!
回答1:
I enjoyed this problem and ran into some troubles coming up with an approach. Enough messing around makes the pattern obvious, though; here's the result:
#include <stdio.h>
#define BLANK " "
#define FILLED "# "
void spiral(int size) {
int i, j;
if (!(size & 1)) { size++; }
int half = size / 2 + 1;
/* top */
for (i = 0; i < half; i++) {
if (i & 1) {
for (j = 0; j < size; j++) {
if (!(j & 1) && (j < i - 1 || j >= size - i)) {
printf(FILLED);
}
else {
printf(BLANK);
}
}
}
else {
for (j = 0; j < size; j++) {
if ((j & 1) && (j < i - 1 || j >= size - i)) {
printf(BLANK);
}
else {
printf(FILLED);
}
}
}
puts("");
}
/* bottom half */
for (; i < size; i++) {
if (i & 1) {
for (j = 0; j < size; j++) {
if (!(j & 1) && (j < size - i || j > i)) {
printf(FILLED);
}
else {
printf(BLANK);
}
}
}
else {
for (j = 0; j < size; j++) {
if ((j & 1) && (j < size - i || j > i)) {
printf(BLANK);
}
else {
printf(FILLED);
}
}
}
puts("");
}
}
int main() {
int i;
for (i = 1; i < 35; i += 2 ) {
spiral(i);
puts("\n");
}
return 0;
}
Output:
#
# # #
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# # # # # # # # # # # # # # # # # # # # # # # # # # # # #
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# # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
# # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
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# #
# # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # # #
Explanation:
Let i represent the current row index and j represent the current column index.
Split the problem into two halves. The bottom half is easier because the left and right halves are symmetrical, so both even and odd rows print their respective pattern on alternating column indices if j < size - i || j > i.
The top half is a little trickier: the pattern is the same, except the left side lags behind the right side by 1, meaning we need to subtract 1 from the left side: if j < i - 1 || j >= size - i.
Note that this code could use some cleanup to reduce repetition; I left it verbose so that it's clear how it works. I also took the liberty of adjusting the characters to print because the original is harder on the eyes--this is easily adjusted using the #defines or adding parameters to the function.
Here's a repl.
来源：https://stackoverflow.com/questions/51691446/how-to-draw-a-spiral-of-with-only-for-while-loops-and-if-else-statements-with