题解 | 染色

#include <iostream>
#include <vector>
using namespace std;

int main() {
    int n, m;
    cin >> n >> m;
    
    vector<int> diff1(n + 2, 0); // 黄色（1）
    vector<int> diff2(n + 2, 0); // 蓝色（2）
    vector<int> diff3(n + 2, 0); // 红色（3）
    
    while (m--) {
        int l, r, k;
        cin >> l >> r >> k;
        if (k == 1) {
            diff1[l]++;
            diff1[r + 1]--;
        } else if (k == 2) {
            diff2[l]++;
            diff2[r + 1]--;
        } else if (k == 3) {
            diff3[l]++;
            diff3[r + 1]--;
        }
    }
    
    int cnt = 0;
    int current1 = 0, current2 = 0, current3 = 0;
    for (int i = 1; i <= n; i++) {
        current1 += diff1[i];
        current2 += diff2[i];
        current3 += diff3[i];
        
        bool hasYellow = current1 > 0;
        bool hasBlue = current2 > 0;
        bool hasRed = current3 > 0;
        
        if (hasYellow && hasBlue && !hasRed) {
            cnt++;
        }
    }
    
    cout << cnt << endl;
    return 0;
}