Snake Game in C about the switch statement - c

Question

It's a simple game,just aim to input a character,move the snake and print the table everytime.
The switch statement in the main function settle 4 cases'a' 's' 'd' 'w' without default,However,when the program is running,if a character out of the cases is input,the program still reacts and output the table(besides,the talbe is output twice).Why?
Besides,it also confused me that the snake don't move correctly if the input is in the cases.
Forgot to add 'break'after cases before:)but the problem still confuse me.Now if I use'break'under default,the program still print the table twice,if I use 'continue'under default,the program won't react to the incorrect input.
But the snake still don't move correctly.:(
#include<stdio.h>
#include<stdlib.h>
#include<time.h>
#define SNAKE_MAX_LENGTH 20
void snakeMove(int, int);
void put_money(void);
void output(void);
void gameover(void);
char map[12][12] =
{"************",
"*XXXXH *",
"* *",
"* *",
"* *",
"* *",
"* *",
"* *",
"* *",
"* *",
"* *",
"************"};
int snakeX[SNAKE_MAX_LENGTH] = {1, 2, 3, 4, 5};
int snakeY[SNAKE_MAX_LENGTH] = {1, 1, 1, 1, 1};
int snakeLength = 5;
int game=1,origin=1,eaten=0;
int main() {
char ch;
srand(time(NULL));
put_money();
output();
origin=0;
while(game) {
scanf("%c",&ch);
switch(ch) {
case 'w':
snakeMove(1,1);
break;
case 's':
snakeMove(2,1);
break;
case 'a':
snakeMove(3,1);
break;
case 'd':
snakeMove(4,1);
break;
default:
continue;
}
if(eaten==1) {
put_money();
eaten=0;
}
output();
}
gameover();
return 0;
}
void snakeMove(int direction, int distance) {
int i,move=1;
switch(direction) {
case 1:
if(snakeY[3]==snakeY[4]+distance)
move=0;
else
snakeY[4]=snakeY[4]+distance;
break;
case 2:
if(snakeY[3]==snakeY[4]-distance)
move=0;
else
snakeY[4]=snakeY[4]-distance;
break;
case 3:
if(snakeX[3]==snakeX[4]-distance)
move=0;
else
snakeX[4]=snakeX[4]-distance;
break;
case 4:
if(snakeX[3]==snakeX[4]+distance)
move=0;
else
snakeX[4]=snakeX[4]+distance;
}
if (move==1) {
for(i=3;i>=0;i--){
snakeX[i]=snakeX[i+1];
snakeY[i]=snakeY[i+1];
}
}
}
void output(void) {
int x, y,i;
if(origin==0) {
for(x=1;x<11;x++) {
for(y=1;y<11;y++) {
if(map[x][y]!='$')
map[x][y]=' ';
}
}
if(map[snakeX[4]][snakeY[4]]=='$')
eaten=1;
for(i=0;i<4;i++)
map[snakeX[i]][snakeY[i]]='X';
map[snakeX[4]][snakeY[4]]='H';
if(snakeX[4]==0||snakeX[4]==11||snakeY[4]==0||snakeY[4]==11)
game=0;
for(i=0;i<4;i++) {
if(snakeX[4]==snakeX[i]&&snakeY[4]==snakeY[i])
game=0;
}
}
for(x=0;x<12;x++) {
for(y=0;y<12;y++)
printf("%c",map[x][y]);
printf("\n");
}
}
void gameover(void) {
printf("Game Over!!!\n");
exit(0);
}
void put_money(void) {
int foodx,foody,done=0;
while(done==0) {
foodx=rand()%12;
foody=rand()%12;
if(map[foodx][foody]==' ') {
map[foodx][foody]='$';
done=1;
}
}
}

Answer 1

Interesting. Your switch statement was fine. Here is a working code with changes commented, followed by a whole code:
#include<stdio.h>
#include<stdlib.h>
#include<time.h>
#define SNAKE_MAX_LENGTH 20
void snakeMove(int, int);
void put_money(void);
void update_snake(void);
void output(void);
void gameover(void);
char map[12][12] =
{"************",
"*XXXXH *",
"* *",
"* *",
"* *",
"* *",
"* *",
"* *",
"* *",
"* *",
"* *",
"************"};
int snakeX[SNAKE_MAX_LENGTH] = {1, 2, 3, 4, 5};
int snakeY[SNAKE_MAX_LENGTH] = {1, 1, 1, 1, 1};
int snakeLength = 5;
int game=1,origin=1,eaten=0;
int main() {
char ch;
srand(time(NULL));
put_money();
output();
origin=0;
while(game) {
As said by Cool guy, a space in scanf works. This is because when you press enter, the newline is counted as a character.
scanf(" %c",&ch);
switch(ch) {
case 'w':
snakeMove(1,1);
break;
case 's':
snakeMove(2,1);
break;
case 'a':
snakeMove(3,1);
break;
case 'd':
snakeMove(4,1);
break;
default:
continue;
}
if(eaten==1) {
put_money();
eaten=0;
}
output();
}
gameover();
return 0;
}
This update function was added because you need to update the snake before you update the head. Otherwise, you'd lose the original head when you try to send it back.
void update_body()
{
int i;
for(i=0;i<4;i++){
snakeX[i]=snakeX[i+1];
snakeY[i]=snakeY[i+1];
}
}
void snakeMove(int direction, int distance) {
int move=1;
switch(direction) {
case 1:
The third issue is that in graphics, the origin, (0, 0) is in the top left corner instead of the bottom left. That means to go up, you have to subtract and to go down you have to add.
if(snakeY[3]==snakeY[4]-distance)
move=0;
else{
update_body();
snakeY[4]=snakeY[4]-distance;
}
break;
case 2:
if(snakeY[3]==snakeY[4]+distance)
move=0;
else{
update_body();
snakeY[4]=snakeY[4]+distance;
}
break;
case 3:
if(snakeX[3]==snakeX[4]-distance)
move=0;
else{
update_body();
snakeX[4]=snakeX[4]-distance;
}
break;
case 4:
if(snakeX[3]==snakeX[4]+distance)
move=0;
else{
update_body();
snakeX[4]=snakeX[4]+distance;
}
}
}
void output(void) {
int x, y,i;
if(origin==0) {
for(x=1;x<11;x++) {
for(y=1;y<11;y++) {
if(map[x][y]!='$')
map[x][y]=' ';
}
}
The last problem is that the map is upside down. This means that the X and Y coordinates were 1st and 2nd, when they should have been 2nd and 1st.
if(map[snakeY[4]][snakeX[4]]=='$')
eaten=1;
for(i=0;i<4;i++)
map[snakeY[i]][snakeX[i]]='X';
map[snakeY[4]][snakeX[4]]='H';
if(snakeX[4]==0||snakeX[4]==11||snakeY[4]==0||snakeY[4]==11)
game=0;
for(i=0;i<4;i++) {
if(snakeX[4]==snakeX[i]&&snakeY[4]==snakeY[i])
game=0;
}
}
for(x=0;x<12;x++) {
for(y=0;y<12;y++)
printf("%c",map[x][y]);
printf("\n");
}
}
void gameover(void) {
printf("Game Over!!!\n");
exit(0);
}
void put_money(void) {
int foodx,foody,done=0;
while(done==0) {
foodx=rand()%12;
foody=rand()%12;
if(map[foodx][foody]==' ') {
map[foodx][foody]='$';
done=1;
}
}
}
Here's the code whole
#include<stdio.h>
#include<stdlib.h>
#include<time.h>
#define SNAKE_MAX_LENGTH 20
void snakeMove(int, int);
void put_money(void);
void update_body();
void output(void);
void gameover(void);
char map[12][12] =
{"************",
"*XXXXH *",
"* *",
"* *",
"* *",
"* *",
"* *",
"* *",
"* *",
"* *",
"* *",
"************"};
int snakeX[SNAKE_MAX_LENGTH] = {1, 2, 3, 4, 5};
int snakeY[SNAKE_MAX_LENGTH] = {1, 1, 1, 1, 1};
int snakeLength = 5;
int game=1,origin=1,eaten=0;
int main() {
char ch;
srand(time(NULL));
put_money();
output();
origin=0;
while(game) {
scanf(" %c",&ch);
switch(ch) {
case 'w':
snakeMove(1,1);
break;
case 's':
snakeMove(2,1);
break;
case 'a':
snakeMove(3,1);
break;
case 'd':
snakeMove(4,1);
break;
default:
continue;
}
if(eaten==1) {
put_money();
eaten=0;
}
output();
}
gameover();
return 0;
}
void update_body()
{
int i;
for(i=0;i<4;i++){
snakeX[i]=snakeX[i+1];
snakeY[i]=snakeY[i+1];
}
}
void snakeMove(int direction, int distance) {
int move=1;
switch(direction) {
case 1:
if(snakeY[3]==snakeY[4]-distance)
move=0;
else{
update_body();
snakeY[4]=snakeY[4]-distance;
}
break;
case 2:
if(snakeY[3]==snakeY[4]+distance)
move=0;
else{
update_body();
snakeY[4]=snakeY[4]+distance;
}
break;
case 3:
if(snakeX[3]==snakeX[4]-distance)
move=0;
else{
update_body();
snakeX[4]=snakeX[4]-distance;
}
break;
case 4:
if(snakeX[3]==snakeX[4]+distance)
move=0;
else{
update_body();
snakeX[4]=snakeX[4]+distance;
}
}
}
void output(void) {
int x, y,i;
if(origin==0) {
for(x=1;x<11;x++) {
for(y=1;y<11;y++) {
if(map[x][y]!='$')
map[x][y]=' ';
}
}
if(map[snakeY[4]][snakeX[4]]=='$')
eaten=1;
for(i=0;i<4;i++)
map[snakeY[i]][snakeX[i]]='X';
map[snakeY[4]][snakeX[4]]='H';
if(snakeX[4]==0||snakeX[4]==11||snakeY[4]==0||snakeY[4]==11)
game=0;
for(i=0;i<4;i++) {
if(snakeX[4]==snakeX[i]&&snakeY[4]==snakeY[i])
game=0;
}
}
for(x=0;x<12;x++) {
for(y=0;y<12;y++)
printf("%c",map[x][y]);
printf("\n");
}
}
void gameover(void) {
printf("Game Over!!!\n");
exit(0);
}
void put_money(void) {
int foodx,foody,done=0;
while(done==0) {
foodx=rand()%12;
foody=rand()%12;
if(map[foodx][foody]==' ') {
map[foodx][foody]='$';
done=1;
}
}
}