Section 1.4,Mother's Milk

1题目描述

http://ace.delos.com/usacoprob2?a=bDgbfJDh5Pw&S=milk3

2解题思路

广度优先搜索，具体如下：

1）搜索状态保存在一个队列中结构体queue中，已经存在的状态保存在一个二维数组statelist中

2）在一个二重循环中产生下一个状态

3）加入队列的条件是下一状态在statelist中不存在。

3代码

/*
ID: wangsiy1
LANG: C
TASK: milk3
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define QLEN 10000
#define LISTLEN 1000
#define DEBUG 0
/* bucket行为队列下标，列为三个筒 */
typedef struct {
    int bucket[QLEN][3];
    int head, tail;
} queue;

int capacity[3];

void printg(queue *q)
{
    int i, j;   
    for(i=q->head; i<q->tail; i++) {
    printf("bucket[%d]:\n", i);
    for(j=0; j<3; j++)
        printf("%d ", q->bucket[i][j]);
    }
    printf("\n");
}

void init(queue *q)
{
    q->head = 0;
    q->tail = 0;
}

int empty(queue *q)
{
    if(q->head==q->tail)
    return 1;
    else
    return 0;
}

int dequeue(queue *q, int *state)
{
    int i;
    if(empty(q))
    return 0;
    else {
    for(i=0; i<3; i++)
        state[i] = q->bucket[q->head][i];
    q->head = (q->head + 1) % QLEN;
    return 1;
    }
}

int enqueue (queue *q, int *state)
{
    int i;
    if((q->tail+1)%QLEN == q->head)
    return 0;
    else {
    for(i=0; i<3; i++)
        q->bucket[q->tail][i] = state[i];
    q->tail = (q->tail+1) % QLEN;
    return 1;
    }
}

int cmp(const void *a, const void *b)
{
    return *(int *)a - *(int *)b;
}

int existresult(int *result, int h, int m)
{
    int i;
    for(i=0; i<m; i++)
    if(result[i]==h)
        return 1;
    return 0;
}

int insertlist(int statelist[][3], int *listlen, int *state)
{
    int i;
    for(i=0; i<3; i++)
    statelist[*listlen][i] = state[i];
    ++(*listlen);
} 

int isinlist(int statelist[][3], int listlen, int *state)
{
    int i, j, f;
    for(i=0; i<listlen; i++) {
    f=1;
    for(j=0; j<3; j++) {
        if(statelist[i][j] != state[j]) {
        f=0;
        break;
        }
    }
    if(f==1)
        return 1;
    }
    return 0;
}

main ()
{
    queue *q;
    int state[3], i, result[1000], resultlen, j, nxtstate[3];
    int statelist[LISTLEN][3], listlen=0;
    FILE *fin  = fopen ("milk3.in", "r");
    FILE *fout = fopen ("milk3.out", "w");

    q = (queue *) malloc(sizeof(queue));
    init(q);
    for(i=0; i<3; i++)
    fscanf(fin, "%d", capacity+i);
    state[0] = 0;
    state[1] = 0;
    state[2] = capacity[2];    
    enqueue(q, state);

    result[0] = state[2];
    resultlen=1;
    insertlist(statelist, &listlen, state);
    while(!empty(q)) {
    if(!dequeue(q, state)) {
        printf("empty queue, cannot dequeue.\n");
        exit(0);
    }
    for(i=0; i<3; i++) {
        if(state[i]!=0) {
        for(j=0; j<3; j++) {
            if(i!=j && state[j]<capacity[j]) {
            nxtstate[0] = state[0];
            nxtstate[1] = state[1];
            nxtstate[2] = state[2];
            if(capacity[j]-state[j]>=state[i]) {
                nxtstate[j] = state[j] + state[i];
                nxtstate[i] = 0;
            } /* if(capacity[j]-state[j]>=state[i]) */
            else {
                nxtstate[j] = capacity[j];
                nxtstate[i] = state[i] - capacity[j] + state[j];
            }

            if(!isinlist(statelist, listlen, nxtstate)) {
#if DEBUG
                printf("%d %d %d\n", nxtstate[0], nxtstate[1], nxtstate[2]);
#endif
                if(nxtstate[0]==0 &&
                   !existresult(result, nxtstate[2], resultlen))
                result[resultlen++] = nxtstate[2];
                enqueue(q, nxtstate);
                insertlist(statelist, &listlen, nxtstate);
            }
            }      /* if(i!=j && state[j]<capacity[j]) */
        }      /* for(j=0; j<3; j++) */
        }          /* if(state[i]!=0) */
    }          /* for(i=0; i<3; i++) */
    }

    qsort(result, resultlen, sizeof(int), cmp);
    for(i=0; i<resultlen; i++) {
    fprintf(fout, "%d", result[i]);
    if(i!=resultlen-1)
        fprintf(fout, " ");
    }
    fprintf(fout, "\n");
    exit (0);
}