Take Your Seat (Floyd)

topic

　　https://nanti.jisuanke.com/t/41288

The meaning of problems

　　N cities given level of risk and a adjacency matrix describing road information. After the interrogation of m, Q (u, v) does not pass through the shortest in the case where w is greater than the degree of danger between urban cities.

answer

　　Bare Floyd, do not drop that kind of dimension. edge [k] [i] [j] indicates that the update with the first k cities. Then the degree of danger according to the first city to row order from small to large, then the edge through such arrays sequentially updated, to update the top-k in FIG cities must not exceed comprises a k-th degree of danger City. Finally, ask for while looking for the greatest city in the k-1 ~ w range just fine.

　　In fact, this question is a naked Floyd, but to be honest it is not enough understanding of Floyd's deep, just stay in the board. . . .

 #include <iostream>
#include <cstring>
#include <string>
#include <algorithm>
#include <cmath>
#include <cstdio>
#include <queue>
#include <stack>
#include <map>
#include <bitset>
#define ull unsigned long long
#define met(a, b) memset(a, b, sizeof(a))
#define lowbit(x) (x&(-x))
#define MID (l + r) / 2
#define ll long long

using namespace std;

const int inf = 0x3f3f3f3f;
const ll INF = 0x3f3f3f3f3f3f3f3f;
const ll mod = 1e6 + 3;
const int maxn = 1e5 + 7;
const int N = 110;

struct node {
    int data, id;
    bool operator < (const node &a) const {
        return data < a.data;
    }
}arr[220];

int edge[220][220][220];

int main() {
    int T, sp = 0;
    scanf("%d", &T);
    while(T--) {
        int n, m;
        scanf("%d%d", &n, &m);
        arr[0].data = 0;
        for(int i = 1; i <= n; i++) {
            scanf("%d", &arr[i].data);
            arr[i].id = i;
        }
        sort(arr+1, arr+1+n);
        for(int i = 1; i <= n; i++) {
            for(int j = 1; j <= n; j++) {
                scanf("%d", &edge[0][i][j]);
            }
        }
        for(int k = 1; k <= n; k++) {
            int t = arr[k].id;
            for(int i = 1; i <= n; i++) {
                for(int j = 1; j <= n; j++) {
                    edge[k][i][j] = min(edge[k-1][i][j], edge[k-1][i][t] + edge[k-1][t][j]);
                }
            }
        }
        printf("Case #%d:\n", ++sp);
        for(int i = 1; i <= m; i++) {
            int u, v, w;
            scanf("%d%d%d", &u, &v, &w);
            int k = 0;
            for(int i = 1; i <= n; i++) 
                if(arr[i].data <= w) k = i;
            printf("%d\n", edge[k][u][v]);
        }
    }
    return 0;
}

 

https://nanti.jisuanke.com/t/41288