POJ 2376 Cleaning Shifts（贪心）

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题目地址：http://poj.org/problem?id=2376

思路：起点为1的选一个最大的，剩下的放到结构体中，排序一下贪心就行

AC代码：

#include <iostream>#include <cstdio>#include <cstdlib>#include <algorithm>#include <queue>#include <stack>#include <map>#include <cstring>#include <climits>#include <cmath>#include <cctype>const int inf = 0x3f3f3f3f;//1061109567typedef long long LL;#define lson l,m,rt<<1#define rson m+1,r,rt<<1|1using namespace std;struct node{    int st;    int ed;}a[25010];int visit[25010];bool cmp(node a,node b){    if(a.ed != b.ed)        return a.ed > b.ed;    else        return a.st < b.st;}int main(){    int n,t;    while(scanf("%d%d",&n,&t) != EOF)    {        int st,ed,l=0,max1 = -1;        for(int i=0; i<n; i++)        {            scanf("%d%d",&st,&ed);            if(st == 1)            {                if(ed > max1)                    max1 = ed;            }            else            {                a[l].st = st;                a[l].ed = ed;                l++;            }        }        if(max1 == -1)        {            printf("-1\n");            continue;        }        sort(a,a+l,cmp);        memset(visit,0,sizeof(visit));        int temp = max1 + 1;        bool flag = true;        int sum = 0;        while(true)        {            sum++;            if(temp > t)                break;            int i;            for(i=0; i<l; i++)            {                if(!visit[i] && a[i].st <= temp)                {                    visit[i] = 1;                    temp = a[i].ed + 1;                    break;                }            }            if(i == l)            {                flag = false;                break;            }        }        if(flag)            printf("%d\n",sum);        else            printf("-1\n");    }    return 0;}

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