用C++写一个BF算法

Sure, here's an example Brainfuck algorithm written in C:

#include <stdio.h>
#include <stdlib.h>

#define MAX_LENGTH 30000    // maximum length of the Brainfuck input string

int main(void) {
    char input[MAX_LENGTH]; // input string for Brainfuck
    int tape[MAX_LENGTH] = {0}; // initialize the Brainfuck tape with all 0's
    int *ptr = tape; // initialize the Brainfuck data pointer to point to the first index of the tape
    int loops[MAX_LENGTH] = {0}; // array to store indices of left brackets in the input string
    int stack[MAX_LENGTH] = {0}; // stack to keep track of nested loops
    int *loop_ptr = loops; // pointer to the current index of the loops array
    int stack_top = 0; // index of the top of the stack
    int i = 0; // index of the current character of the input string

    // prompt the user for a Brainfuck input string
    printf("Enter a Brainfuck program:\n");
    fgets(input, MAX_LENGTH, stdin);

    // process each character of the input string
    while (input[i] != '\0') {
        switch (input[i]) {
        case '>':
            ptr++;
            break;
        case '<':
            ptr--;
            break;
        case '+':
            (*ptr)++;
            break;
        case '-':
            (*ptr)--;
            break;
        case '.':
            putchar(*ptr);
            fflush(stdout);
            break;
        case ',':
            *ptr = getchar();
            break;
        case '[':
            if (*ptr == 0) {
                // skip the loop
                i = stack[stack_top] - 1;
                stack_top--;
            } else {
                // add the current index to the loops array and push it onto the stack
                *loop_ptr = i;
                loop_ptr++;
                stack_top++;
                stack[stack_top] = i;
            }
            break;
        case ']':
            if (*ptr != 0) {
                // jump back to the beginning of the loop
                i = *(loop_ptr - 1);
            } else {
                // pop the loop off the stack
                loop_ptr--;
                stack_top--;
            }
            break;
        }
        i++;
    }

    return 0;
}

This program prompts the user for a Brainfuck input string, then executes it using an array of integers as the tape and a pointer to the current data position on the tape. It also handles loops using a stack to keep track of nested brackets. Note that this implementation assumes that the input string contains a valid Brainfuck program and does not perform any error checking.