hdu 1051 (greedy algorithm, how a little modification turn 15ms to 0ms) 分类： hdoj 2015-06-18 12:54 29人阅读 评论(0) 收藏

the 2 version are essentially the same, except version 2 search from the larger end, which reduce the search time in extreme condition from linear to constant, so be faster.

version 1

#include <cstdio>
#include <algorithm>

struct LWPair{
    int l,w;
};

int main() {
    //freopen("input.txt","r",stdin);
    const int MAXSIZE=5000, MAXVAL=10000;
    LWPair sticks[MAXSIZE];
    int store[MAXSIZE];
    int ncase, nstick, length,width, tmp, time, i,j;
    if(scanf("%d",&ncase)!=1) return -1;
    while(ncase-- && scanf("%d",&nstick)==1) {
        for(i=0;i<nstick;++i) scanf("%d%d",&sticks[i].l,&sticks[i].w);
        std::sort(sticks,sticks+nstick,[](const LWPair &lhs, const LWPair &rhs) { return lhs.l>rhs.l || lhs.l==rhs.l && lhs.w>rhs.w; });
        for(time=-1,i=0;i<nstick;++i) {
            tmp=sticks[i].w;
            for(j=0;j<=time && store[j]<tmp;++j) ; //search from left to right
            if(j>time) { store[++time]=tmp; }
            else { store[j]=tmp; }
        }
        printf("%d\n",time+1);
    }
    return 0;
}

version 2

#include <cstdio>
#include <algorithm>

struct LWPair{
    int l,w;
};

int main() {
    //freopen("input.txt","r",stdin);
    const int MAXSIZE=5000, MAXVAL=10000;
    LWPair sticks[MAXSIZE];
    int store[MAXSIZE];
    int ncase, nstick, length,width, tmp, time, i,j;
    if(scanf("%d",&ncase)!=1) return -1;
    while(ncase-- && scanf("%d",&nstick)==1) {
        for(i=0;i<nstick;++i) scanf("%d%d",&sticks[i].l,&sticks[i].w);
        std::sort(sticks,sticks+nstick,[](const LWPair &lhs, const LWPair &rhs) { return lhs.l>rhs.l || lhs.l==rhs.l && lhs.w>rhs.w; });
        for(time=-1,i=0;i<nstick;++i) {
            tmp=sticks[i].w;
            for(j=time;j>=0 && store[j]>=tmp;--j) ; // search from right to left
            if(j==time) { store[++time]=tmp; }
            else { store[j+1]=tmp; }
        }
        printf("%d\n",time+1);
    }
    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.