poj 2376

http://acm.pku.edu.cn/JudgeOnline/problem?id=2376

在T天里干完一件事，有多只牛，每只牛负责连续几天，日期可能重叠。找出最少数量的牛干完这件事。（可能讲的不清楚）

 

#include<stdio.h> 
#include<algorithm> 
using namespace std; 
struct ORDER 
{ 
    int left; 
    int right; 
}order[25001]; 

bool cmp(ORDER a, ORDER b) 
{ 
    return a.left < b.left; 
} 

int main() 
{ 
    int n_cow, time, i, step, find, tot, ok, temp_right; 
    while(scanf("%d%d", &n_cow, &time)!=EOF) 
    { 
        for(i=0; i<n_cow; i++) 
            scanf("%d%d", &order[i].left, &order[i].right); 
        sort(order, order + n_cow, cmp); 

        if(order[0].left >1) 
        { 
            printf("-1\n"); 
            continue; 
        } 
         
        step = 0; 
        i = 0; 
        ok = 1; 
        tot = 0; 

        while(step < time && i < n_cow) 
        { 
            find = 0; 
            temp_right = 0; 
            while(order[i].left <= step + 1 && i < n_cow ) 
            { 
                find = 1; 
                if(order[i].right > temp_right) 
                    temp_right = order[i].right; 
                i++; 
            } 
            if(!find) 
            { 
                ok = 0; 
                break; 
            } 
            step = temp_right; 
            tot++; 
        } 
        if(!ok || step < time) 
            printf("-1\n"); 
        else 
            printf("%d\n", tot); 
    } 
    return 0; 
}