python/TangDou/AcWing_TiGao/T4/239_ExtendDomain_Static_ErFen.cpp

#include <bits/stdc++.h>
using namespace std;

const int N = 40010, B = N / 2;

// 结构体记录原始输入
struct Node {
    int x, y, e;
} g[N];

int n, m;

// 离散化静态数组+二分查找新位置
int b[N], bl;
int get(int x) {
    return lower_bound(b, b + bl, x) - b;
}

// 并查集
int p[N];
int find(int x) {
    if (p[x] != x) p[x] = find(p[x]);
    return p[x];
}

int main() {
    scanf("%d %d", &n, &m);
    n = 0;
    for (int i = 1; i < N; i++) p[i] = i;

    for (int i = 1; i <= m; i++) {
        int x, y;
        char t[100];
        scanf("%d %d %s", &x, &y, t);

        g[i].x = x, g[i].y = y;
        if (t[0] == 'e')
            g[i].e = 0;
        else
            g[i].e = 1;

        // 记录下来
        b[bl++] = x, b[bl++] = y;
    }

    // 离散化去重
    sort(b, b + 2 * m);
    bl = unique(b, b + 2 * m) - b;

    int res = m;
    for (int i = 1; i <= m; i++) {
        int a = g[i].x, b = g[i].y, e = g[i].e;
        a = get(a - 1), b = get(b);       // 计算出新的在并查集中的号
        if (e == 0) {                     // 偶数个1
            if (find(a + B) == find(b)) { // 如果奇偶性不同，因为b与a+B相同
                res = i - 1;
                break;
            }
            // join两个奇偶相同的集合
            p[find(a)] = find(b);
            p[find(a + B)] = find(b + B);
        } else { // 奇数个1
            if (find(a) == find(b)) {
                res = i - 1;
                break;
            }
            // join两个奇偶不相同的集合
            p[find(a + B)] = find(b);
            p[find(a)] = find(b + B);
        }
    }
    printf("%d\n", res);
    return 0;
}