zoj 3197

 

http://acm.zju.edu.cn/onlinejudge/showProblem.do?problemId=3322

 

最小区间覆盖，排序加上贪心。

 

 

#include <iostream> #include <algorithm> #include <cstdio> using namespace std; struct SetNode{ int a; int b; }mySet[5010]; int n; int minPoint; int maxPoint; bool cmp(SetNode a, SetNode b){ if(a.a != b.a) return a.a < b.a; return a.b < b.b; } int work(){ int cur = minPoint; int i = 0; int sum = 0; while(cur <= maxPoint && i < n){ int temp = cur; while(cur >= mySet[i].a){ if(temp < mySet[i].b) temp = mySet[i].b; i++; } cur = temp + 1; sum++; } return sum; } int main(){ int t; scanf("%d", &t); while(t--){ scanf("%d", &n); minPoint = 1000000; maxPoint = -1; for(int i = 0; i < n; i++){ scanf("%d%d", &mySet[i].a, &mySet[i].b); if(mySet[i].a < minPoint) minPoint = mySet[i].a; if(mySet[i].b > maxPoint) maxPoint = mySet[i].b; } sort(mySet, mySet + n, cmp); cout << work() << endl; } }