【HDOJ】2363 Cycling

二分+Dijkstra。

  1 #include <iostream>
  2 #include <cstdio>
  3 #include <cstring>
  4 #include <algorithm>
  5 #include <queue>
  6 using namespace std;
  7
  8 #define MAXN 105
  9 #define INF  1000001
 10
 11 int n, m;
 12 int map[MAXN][MAXN], al[MAXN], bk[MAXN], path[MAXN];
 13 bool visit[MAXN];
 14 int low, high;
 15 int ans, dif;
 16
 17 int dijkstra() {
 18     int i, j, v, min;
 19
 20     if (al[1]<low || al[1]>high)
 21         return INF;
 22
 23     memset(visit, false, sizeof(visit));
 24     visit[1] = true;
 25     for (i=1; i<=n; ++i) {
 26         if (al[i]>=low && al[i]<=high)
 27             path[i] = map[1][i];
 28         else
 29             path[i] = INF;
 30     }
 31
 32     for (i=1; i<n; ++i) {
 33         min = INF;
 34         for (j=1; j<=n; ++j) {
 35             if (!visit[j] && path[j]<min) {
 36                 v = j;
 37                 min = path[j];
 38             }
 39         }
 40         if (min == INF)
 41             break;
 42         visit[v] = true;
 43         for (j=1; j<=n; ++j) {
 44             if (!visit[j] && map[v][j]+min<path[j] && al[j]>=low && al[j]<=high)
 45                 path[j] = map[v][j] + min;
 46         }
 47     }
 48     return path[n];
 49 }
 50
 51 int main() {
 52     int t, min, l, r, max, mid;
 53     int i, j, k, tmp;
 54
 55     scanf("%d", &t);
 56     while (t--) {
 57         scanf("%d %d", &n, &m);
 58         min = dif = 1000000001;
 59         ans = INF;
 60         max = 0;
 61         for (i=1; i<=n; ++i) {
 62             scanf("%d", &al[i]);
 63             if (al[i] < min) min = al[i];
 64             if (al[i] > max) max = al[i];
 65             bk[i] = al[i];
 66         }
 67         for (i=1; i<=n; ++i) {
 68             map[i][i] = 0;
 69             for (j=i+1; j<=n; ++j)
 70                 map[i][j] = map[j][i] = INF;
 71         }
 72         while (m--) {
 73             scanf("%d %d %d", &i, &j, &k);
 74             if (map[i][j] > k)
 75                 map[i][j] = map[j][i] = k;
 76         }
 77         sort(bk+1, bk+1+n);
 78         l = 0; r = max-min+1;
 79         while (l < r) {
 80             mid = (l + r)>>1;
 81             bool flag = false;
 82             for (i=1; i<=n; ++i) {
 83                 low = bk[i];
 84                 high = bk[i] + mid;
 85                 tmp = dijkstra();
 86                 if (tmp != INF) {
 87                     flag = true;
 88                     break;
 89                 }
 90             }
 91             if ( flag ) {
 92                 if (mid < dif) {
 93                     dif = mid;
 94                     ans = tmp;
 95                 } else if (mid==dif && ans > tmp) {
 96                     ans = tmp;
 97                 }
 98                 r = mid;
 99             } else {
100                 l = mid + 1;
101             }
102         }
103         printf("%d %d\n", dif, ans);
104     }
105
106     return 0;
107 }

【HDOJ】2363 Cycling