kuangbin专题专题四 MPI Maelstrom POJ

题目链接：https://vjudge.net/problem/POJ-1502

dijkstra板子题，题目提供下三角情况，不包含正对角线，因为有题意都为0，处理好输入，就是一个很水的题。

 1 #include <iostream>
 2 #include <cstring>
 3 #include <algorithm>
 4 #include <cstdio>
 5 #include <string>
 6 #include <vector>
 7 using namespace std;
 8  
 9 typedef long long LL;
10 #define inf (1LL << 30) - 1
11 #define rep(i,j,k) for(int i = (j); i <= (k); i++)
12 #define rep__(i,j,k) for(int i = (j); i < (k); i++)
13 #define per(i,j,k) for(int i = (j); i >= (k); i--)
14 #define per__(i,j,k) for(int i = (j); i > (k); i--)
15 
16 const int N = 110;
17 vector<pair<int,int> > G[N];
18 int val[N];
19 int vis[N];
20 int n;
21 
22 int fun(string& x){
23     int sum = 0;
24 
25     rep__(i,0,(int)x.length()) sum = sum * 10 + (x[i] - '0');
26 
27     return sum;
28 }
29 
30 void input(){
31 
32     string w;
33     rep(i,2,n){
34         rep__(j,1,i){
35             cin >> w;
36 
37             if(w[0] == 'x') continue;
38             int W = fun(w);
39             G[i].push_back(make_pair(j,W));
40             G[j].push_back(make_pair(i,W));
41         }
42     }
43 }
44 
45 int dijkstra(){
46 
47     if(n == 1) return 0;
48     val[1] = 0;
49     rep(i,2,n) val[i] = inf;
50     
51     rep__(i,0,(int)G[1].size()) val[G[1][i].first] = G[1][i].second;
52     vis[1] = true;
53 
54     rep(i,2,n){
55 
56         int x = -1;
57         int v = inf;
58 
59         rep(j,1,n){
60             if(!vis[j] && v > val[j]) v = val[x = j];
61         }
62 
63         if(x == -1) continue;
64         vis[x] = true;
65 
66         rep__(o,0,(int)G[x].size()){
67             int v = G[x][o].first;
68             int w = G[x][o].second;
69             if(!vis[v] && val[v] > val[x] + w)
70                 val[v] = val[x] + w;
71         }
72     }
73 
74     int ans = 0;
75     rep(i,2,n) ans = max(ans, val[i]);
76 
77     return ans;
78 }
79 
80 int main(){
81  
82     ios::sync_with_stdio(false);
83     cin.tie(0);
84 
85     cin >> n;
86     input();
87     cout << dijkstra() << endl;
88 
89     getchar();getchar();
90     return 0;
91 }