A1046. Shortest Distance
The task is really simple: given N exits on a highway which forms a simple cycle, you are supposed to tell the shortest distance between any pair of exits.
Input Specification:
Each input file contains one test case. For each case, the first line contains an integer N (in [3, 105]), followed by N integer distances D1 D2 ... DN, where Di is the distance between the i-th and the (i+1)-st exits, and DNis between the N-th and the 1st exits. All the numbers in a line are separated by a space. The second line gives a positive integer M (<=104), with M lines follow, each contains a pair of exit numbers, provided that the exits are numbered from 1 to N. It is guaranteed that the total round trip distance is no more than 107.
Output Specification:
For each test case, print your results in M lines, each contains the shortest distance between the corresponding given pair of exits.
Sample Input:
5 1 2 4 14 9 3 1 3 2 5 4 1
Sample Output:
3 10 7
1 #include<cstdio> 2 #include<iostream> 3 #include<vector> 4 #include<algorithm> 5 using namespace std; 6 int main(){ 7 int N, M, sum = 0; 8 vector<int> dst2src, re; 9 scanf("%d", &N); 10 int temp = 0; 11 dst2src.push_back(temp); 12 for(int i = 0; i < N; i++){ 13 scanf("%d", &temp); 14 sum += temp; 15 dst2src.push_back(sum); 16 } 17 scanf("%d", &M); 18 for(int i = 0; i < M; i++){ 19 int a, b, L1, L2; 20 scanf("%d%d", &a, &b); 21 if(a > b) swap(a, b); 22 L1 = dst2src[b - 1] - dst2src[a - 1]; 23 L2 = sum - L1; 24 printf("%d\n", min(L1, L2)); 25 } 26 return 0; 27 }
总结:1、可使用swap、min函数,引用algorithm即可。
2、预处理:模拟题一般要考虑到时间复杂度,本题中有N个节点。若不做预处理,M组查询,会有M*N的复杂度。若在读入数据的时候,就计算出源点到该点的距离,则在查询时,a到b的距离可用a到源减去b到源,不用遍历。
3、由于是一个环,a到b的距离只有顺逆时针两种可能。