递归 DFS

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

int sum = 0;

char ch[3] =  {'L', 'R','P'};

void DFS(int x, int n, int t )
{   
    int i;
    
    if (n == t) {
        sum += x;
        return ;
    }
    for (i = 0; i < 3; i++)
        if( ch[i] == 'L')
            DFS(2 * x , n + 1, t);
        else if ( ch[i] == 'R')
            DFS(2 * x + 1, n + 1, t);
        else if ( ch[i] == 'P')
            DFS(x, n + 1, t);
}

int main( )
{
    int i, j, len;
    char ch[20];
    while (scanf("%s", ch) != EOF)
    {
        len = strlen(ch);
        DFS(1, 0, len);
        printf("%d\n",sum);
        sum = 0;
    }
    return 0;
}