算法
线性基
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#include<iostream>
#include<cstring>

using namespace std;

typedef long long LL;

const int N = 50010, M = 70;

LL h[4 * N], ne[4 * N], e[4 * N], w[4 * N], idx;

LL p[M];

LL dis[N];
bool st[N];
int n, m;

void add(LL a, LL b, LL c) {
    e[idx] = b;
    w[idx] = c;
    ne[idx] = h[a];
    h[a] = idx ++;
}

// 注意最多是从63位开始，从64位开始就会发生溢出。
void insert(LL x) {
    for(int i = 63; ~i; i --) {
        if(x >> i & 1) { //这位是1才进行操作
            if(p[i]) 
                x ^= p[i];
            else {
                p[i] = x;
                break;
            }
        }
    }

}

void dfs(LL x, LL res) {
    dis[x] = res;
    st[x] = true;
    for(int i = h[x]; i != -1; i = ne[i]) {
        int j = e[i];
        if(!st[j]) {
            dfs(j, res ^ w[i]);
        }
        else 
            insert(res ^ w[i] ^ dis[j]); 
    }
}

int main() {
    cin >> n >> m;
    
    memset(h, -1, sizeof(h));
    
    while(m --) {
        LL a, b, c;
        scanf("%lld%lld%lld", &a, &b, &c);
        add(a, b, c);
        add(b, a, c);
        
    }
    
    dfs(1, 0);
    
    LL res = dis[n];

    for(int i = 64; ~i; i --) 
        if((res ^ p[i]) > res) 
            res ^= p[i];
    
    cout << res << endl;
    
    return 0;
}