poj2376 Cleaning Shifts（区间贪心，理解题意）
https://vjudge.net/problem/POJ-2376
题意理解错了！！真是要仔细看题啊！！
看了poj的discuss才发现，如果前一头牛截止到3，那么下一头牛可以从4开始！！！
1 #include<iostream> 2 #include<cstdio> 3 #include<queue> 4 #include<cstring> 5 #include<algorithm> 6 #include<cmath> 7 #include<set> 8 #define INF 0x3f3f3f3f 9 typedef long long ll; 10 using namespace std; 11 typedef struct{ 12 int x, y; 13 }Node; 14 Node node[100010]; 15 bool cmp(const Node a, const Node b) 16 { 17 if(a.x != b.x) 18 return a.x<b.x; 19 else 20 return a.y>b.y; 21 }//起点相同则返回终点大的，否则返回起点小的 22 int main() 23 { 24 int n, t, cnt=1, flag=0; 25 cin >> n >> t; 26 for(int i = 0; i < n; i++){ 27 cin >> node[i].x >> node[i].y; 28 } 29 sort(node, node+n, cmp); 30 if(node[0].x != 1){ 31 cout << "-1" << endl; 32 return 0; 33 } 34 else if(node[0].y == t){ 35 cout << "1" << endl; 36 return 0; 37 } 38 else { 39 int end = node[0].y, pre, maxm = node[0].y; 40 for(int i = 1; i < n; i++){ 41 pre = maxm; 42 while(i < n&&node[i].x<=end+1){//这里理解错了！！ 43 if(maxm < node[i].y){ 44 maxm = node[i].y; 45 } 46 i++; 47 } 48 i--; 49 //cout << maxm << endl; 50 if(maxm == t){ 51 cnt++; 52 flag=1; 53 break; 54 } 55 else if(pre == maxm){ 56 break; 57 } 58 else{ 59 end = maxm; 60 cnt++; 61 } 62 } 63 if(!flag) cout << "-1" << endl; 64 else 65 cout << cnt << endl; 66 } 67 return 0; 68 }
