The Two Routes

The Two Routes

思路

超級水題，創建兩個圖就行，一個是火車的，一個是公交車的，而後跑兩遍floyed。

代碼

#include<bits/stdc++.h>

using namespace std;

const int INF = 0x3f3f3f3f;
const int N = 410;

int a[N][N], b[N][N], n, m;

void init() {
    for(int i = 1; i <= n; i++)
        for(int j = 1; j <= n; j++)
            if(i != j)
                a[i][j] = b[i][j] = INF;
}

int main() {
    // freopen("in.txt", "r", stdin);
    int x, y;
    scanf("%d %d", &n, &m);
    init();
    for(int i = 0; i < m; i++) {
        scanf("%d %d", &x, &y);
        a[x][y] = a[y][x] = 1;
    }
    for(int i = 1; i <= n; i++)
        for(int j = 1; j <= n; j++)
            if(a[i][j] == INF)
                b[i][j] = 1;
    for(int k = 1; k <= n; k++)
        for(int i = 1; i <= n; i++)
            for(int j = 1; j <= n; j++)
                if(a[i][k] + a[k][j] < a[i][j])
                    a[i][j] = a[i][k] + a[k][j];
    for(int k = 1; k <= n; k++)
        for(int i = 1; i <= n; i++)
            for(int j = 1; j <= n; j++)
                if(b[i][k] + b[k][j] < b[i][j])
                    b[i][j] = b[i][k] + b[k][j];
    if(a[1][n] == INF || b[1][n] == INF)    puts("-1");
    else    printf("%d\n", max(a[1][n], b[1][n]));
    return 0;
}