[UVa] 101 - The Blocks Problem

uva_101.cpp

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

using std::stack;

#define N 25
int pos[N];
stack<int> pile[N];

void reset_until(int a){
    for(int top = pile[pos[a]].top(); top != a; top = pile[pos[a]].top()){
        pile[pos[a]].pop();
        pile[top].push(top);
        pos[top] = top;
    }
}
void pile_over(int a, int b){
    int top;
    stack<int> buffer;
    do{
        top = pile[pos[a]].top();
        buffer.push(top);
        pile[pos[a]].pop();
    }while(top != a);
    while(!buffer.empty()){
        pile[pos[b]].push(buffer.top());
        pos[buffer.top()] = pos[b];
        buffer.pop();
    }
}

int main(){
    int n, i, a, b;
    char cmd1[10], cmd2[10];
    stack<int> tmp;

    while(scanf("%d", &n) != EOF){
        for(i = 0; i < n; ++i){
            pos[i] = i;
            while(!pile[i].empty())
                pile[i].pop();
            pile[i].push(i);
        }
        while(scanf("%s", cmd1) != EOF){
            if(strcmp(cmd1, "quit") == 0)
                break;
            scanf("%d%s%d", &a, cmd2, &b);
            if(pos[a] == pos[b])
                continue;
            if(strcmp(cmd1, "move") == 0)
                reset_until(a);
            if(strcmp(cmd2, "onto") == 0)
                reset_until(b);
            pile_over(a, b);
        }
        while(!tmp.empty())
            tmp.pop();
        for(i = 0; i < n; ++i){
            while(!pile[i].empty()){
                tmp.push(pile[i].top());
                pile[i].pop();
            }
            printf("%d:", i);
            while(!tmp.empty()){
                printf(" %d", tmp.top());
                tmp.pop();
            }
            putchar('\n');
        }
    }
    return 0;
}