Integer Intervals
| Time Limit: 1000MS | Memory Limit: 10000K | |
| Total Submissions: 11782 | Accepted: 4964 |
Description
An integer interval [a,b], a < b, is a set of all consecutive integers beginning with a and ending with b.
Write a program that: finds the minimal number of elements in a set containing at least two different integers from each interval.
Write a program that: finds the minimal number of elements in a set containing at least two different integers from each interval.
Input
The first line of the input contains the number of intervals n, 1 <= n <= 10000. Each of the following n lines contains two integers a, b separated by a single space, 0 <= a < b <= 10000. They are the beginning and the end of an interval.
Output
Output the minimal number of elements in a set containing at least two different integers from each interval.
Sample Input
4 3 6 2 4 0 2 4 7
Sample Output
4
#include<iostream> #include<cstdio> #include<cstring> #include<map> #include<cmath> #include<vector> #include<algorithm> #include<set> #include<string> #include<queue> #include <stack> using namespace std; #pragma warning(disable : 4996) const int MAXN = 10005; const int INF = 999999; typedef struct Node { int v;//终点位置 int value;//权值 int next;//同一起点下在edge数组中的位置 }Node; Node edge[MAXN * 4];//邻接表 int first[MAXN];//以该点为起点的第一条边在edge数组中的位置 int n; //n点数 bool visited[MAXN]; int dist[MAXN]; queue<int>Q; int MIN, MAX; void init() { int x, y, index; memset(first, -1, sizeof(first)); index = 1; MIN = INF; MAX = -INF; for (int i = 1; i <= n; i++) { scanf("%d %d", &x, &y); y++; if(x < MIN) { MIN = x; } if(y > MAX) { MAX = y; } edge[index].v = y; edge[index].value = 2; edge[index].next = first[x]; first[x] = index++; } //cout << MIN << " " << MAX << endl; for (int i = MIN; i < MAX; i++) { edge[index].v = i + 1; edge[index].value = 0; edge[index].next = first[i]; first[i] = index++; edge[index].v = i; edge[index].value = -1; edge[index].next = first[i + 1]; first[i + 1] = index++; } } void SPFA(int Start) { while (!Q.empty()) { Q.pop(); } for (int i = 0; i <= MAX; i++) { visited[i] = false; dist[i] = -INF; } dist[Start] = 0; visited[Start] = true; Q.push(Start); while (!Q.empty()) { int top = Q.front(); Q.pop(); visited[top] = false; for (int i = first[top]; i != -1 ; i = edge[i].next) { int e = edge[i].v; if(dist[e] < edge[i].value + dist[top]) { dist[e] = edge[i].value + dist[top]; if(!visited[e]) { Q.push(e); visited[e] = true; } } } } } int main() { freopen("in.txt", "r", stdin); while (scanf("%d", &n) != EOF) { init(); SPFA(MIN); printf("%d\n", dist[MAX]); //print(); } return 0; }