hdu 1053 (huffman coding, greedy algorithm, std::partition, std::priority_queue ) 分类： hdoj 2015-06-18 19:11 22人阅读 评论(0) 收藏

huffman coding, greedy algorithm.
std::priority_queue, std::partition,
when i use the three commented lines, excution time increase to 15ms from 0ms, due to worse locality?
thanks to
http://acm.hdu.edu.cn/discuss/problem/post/reply.php?action=support&postid=5699&messageid=2&deep=1
for the provided test case. below is an excerpt,
input
AAAAABCD
THE_CAT_IN_THE_HAT
A
ABCD
AAAAA
ABCDEFGH
END

output
64 13 4.9
144 51 2.8
8 1 8.0
32 8 4.0
40 5 8.0
64 24 2.7

#include <cstdio>
#include <queue>
#include <algorithm>
#include <functional>

int main() {
    //freopen("input.txt","r",stdin);
    const int MAXSIZE=256;
    char line[MAXSIZE], *q;
    //int times[MAXSIZE]={0}, i,tmp,len, sum,res, *p,*pu=times+1,*pn=times+(2-'0'),*pc=times+(12-'A');
    int times[MAXSIZE]={0}, i,tmp,len, sum,res, *p,*pu=times+1,*pn=times+2,*pc=times+12;
    std::priority_queue<int, std::vector<int>, std::greater<int> > my_min_heap;
    while(scanf("%256s",line)==1 && strcmp(line,"END")!=0) {
        for(q=line;tmp=*q;++q) {
            //if(tmp>='A' && tmp<='Z') ++pc[tmp];
            //else if(tmp>='0' && tmp<='9') ++pn[tmp];
            if(tmp>='A' && tmp<='Z') ++pc[tmp-'A'];
            else if(tmp>='0' && tmp<='9') ++pn[tmp-'0'];
            else ++*pu;
        }
        p=std::partition(pu,pu+37,[](int i) { return i>0; });
        len=p-pu;
        if(len<2) { res=strlen(line); }
        else {
            while(--p!=times) my_min_heap.push(*p);
            for(res=0,i=1;i<len;++i) {
                sum=my_min_heap.top(); my_min_heap.pop();
                sum+=my_min_heap.top(); my_min_heap.pop();
                my_min_heap.push(sum);
                res+=sum;
            }
            my_min_heap.pop();
        }
        std::fill(pu,pu+len,0);
        len=strlen(line)<<3;
        printf("%d %d %.1f
",len,res,(double)len/res);
    }
    return 0;
}

版权声明：本文为博主原创文章，未经博主允许不得转载。// p.s. If in any way improment can be achieved, better performance or whatever, it will be well-appreciated to let me know, thanks in advance.