ACM学习历程——POJ 2376 Cleaning Shifts（贪心）

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <algorithm>
#include <set>
#include <map>
#include <vector>
#include <queue>
#include <string>
#define inf 0x3fffffff
#define eps 1e-10

using namespace std;

struct node
{
    int Begin, End;
}a[25005];

bool cmp(node x, node y)
{
    if (x.Begin != y.Begin)
        return x.Begin < y.Begin;
    else
        return x.End > y.End;
}

int t, n;

int qt()
{
    int ans = 0;
    int now, p, k = 0, Max;
    now = 1;
    while (now <= t)
    {
        if (k == n)
            return -1;
        if (a[k].Begin > now)
            return -1;
        Max = a[k].End;
        while (a[k].Begin <= now && k < n)
        {
            Max = max(Max, a[k].End);
            k++;
        }
        now = Max + 1;
        ans++;
    }
    return ans;
}

int main()
{
    //freopen("test.txt", "r", stdin);
    while (scanf("%d%d", &n, &t) != EOF)
    {
        for (int i = 0; i < n; ++i)
            scanf("%d%d", &a[i].Begin, &a[i].End);
        sort(a, a+n, cmp);
        printf("%d\n", qt());
    }
    return 0;
}