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/*
a brainfuck interpreter
reference: https://gist.github.com/maxcountryman/1699708
*/
// tape, input buffer, and read/write pointer
const int TAPE_LEN = 65536, BUFFER_LEN = 32768;
int tape[TAPE_LEN], program[BUFFER_LEN], ptr = 0;
// read the input program
void read_program() {
int i = 0, len = getint();
while (i < len) {
program[i] = getch();
i = i + 1;
}
program[i] = 0;
}
// interpret the input program
void interpret(int input[]) {
int cur_char, loop, i = 0;
while (input[i]) {
cur_char = input[i];
if (cur_char == 62) {
// '>'
ptr = ptr + 1;
}
else if (cur_char == 60) {
// '<'
ptr = ptr - 1;
}
else if (cur_char == 43) {
// '+'
tape[ptr] = tape[ptr] + 1;
}
else if (cur_char == 45) {
// '-'
tape[ptr] = tape[ptr] - 1;
}
else if (cur_char == 46) {
// '.'
putch(tape[ptr]);
}
else if (cur_char == 44) {
// ','
tape[ptr] = getch();
}
else if (cur_char == 93 && tape[ptr]) {
// ']'
loop = 1;
while (loop > 0) {
i = i - 1;
cur_char = input[i];
if (cur_char == 91) {
// '['
loop = loop - 1;
}
else if (cur_char == 93) {
// ']'
loop = loop + 1;
}
}
}
i = i + 1;
}
}
int main() {
read_program();
interpret(program);
return 0;
}
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