POJ 2376 Cleaning Shifts

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简单贪心，trick蛮多的，调了许久~~~

#include <cstdio>#include <cstdlib>#include <cstring>#include <iostream>#include <algorithm>using namespace std;const int MAXN = 25010;const int INF = 0x3f3f3f3f;struct Node{    int l, r;    Node() {}    Node(int t_l, int t_r) : l(t_l), r(t_r) {}    friend bool operator < (const Node &p1, const Node &p2)    {        if(p1.l == p2.l)            return p1.r > p2.r;        return p1.l < p2.l;    }}p[MAXN];int N, T, total, ans;int main(){    //freopen("aa.in", "r", stdin);    //freopen("bb.out", "w", stdout);    while(scanf("%d %d", &N, &T) != EOF)    {        for(int i = 0; i < N; ++i)        {            scanf("%d %d", &p[i].l, &p[i].r);        }        sort(p, p + N);        if(p[0].l > 1)        {            printf("-1\n");        }        else        {            int id = 0;            total = 0; ans = 0;            bool flag = true;            while(id < N)            {                total++;                int t_max = -INF;                flag = false;                while(p[id].l <= total && id < N)                {                    t_max = max(t_max, p[id].r);                    id++;                    flag = true;                }                if(!flag)                    break;                total = t_max, ans++;                if(total >= T) break;            }            if(!flag || total < T)                printf("-1\n");            else                printf("%d\n", ans);        }    }    return 0;}