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A - Rock-paper-scissors Editorial by en_translator

If you are new to learning programming and do not know where to start, please try Problem A “Welcome to AtCoder” from practice contest. There you can find a sample code for each language.

In this problem the value to output is dependent on the inputs $$x$$ and $$y$$. Since there are $$9$$ combinations of possible input, one can enumerate every patterns and make a conditional branch with if statement.

Sample code (C)

int main(){
int x, y;
scanf("%d %d", &x, &y);
if(x==0 && y==0) puts("0");
if(x==0 && y==1) puts("2");
if(x==0 && y==2) puts("1");
if(x==1 && y==0) puts("2");
if(x==1 && y==1) puts("1");
if(x==1 && y==2) puts("0");
if(x==2 && y==0) puts("1");
if(x==2 && y==1) puts("0");
if(x==2 && y==2) puts("2");
}

One can decrease the number of conditional branches by simplifying into “output $$x$$ if $$x$$ and $$y$$ are equal” and “output the value other than $$x$$ and $$y$$ if $$x$$ and $$y$$ are unequal.”

Sample code 2 (C)

int main(){
int x, y;
scanf("%d %d", &x, &y);
if(x==y) printf("%d", x);
else printf("%d", 3-x-y);
}

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