牛客练习赛26

C 城市规划

ps：想复杂了，记录每个点靠的最近的左端点和枚举到这个点时，上次切割的位置。（每次切割都切右端点）

namespace fastIO {
    #define BUF_SIZE 100000
    bool IOerror = 0;
    inline char nc() {
        static char buf[BUF_SIZE], *p1 = buf + BUF_SIZE, *pend = buf + BUF_SIZE;
        if(p1 == pend) {
            p1 = buf;
            pend = buf + fread(buf, 1, BUF_SIZE, stdin);
            if(pend == p1) {
                IOerror = 1;
                return -1;
            }
        }
        return *p1++;
    }
    inline bool blank(char ch) {
        return ch == ' ' || ch == '\n' || ch == '\r' || ch == '\t';
    }
    inline void read(int &x) {
        char ch;
        while(blank(ch = nc()));
        if(IOerror) return;
        for(x = ch - '0'; (ch = nc()) >= '0' && ch <= '9'; x = x * 10 + ch - '0');
    }
    #undef BUF_SIZE
};
using namespace fastIO;

const int N = 1000005;

int n, m;
int a[N];

int main()
{
    read(n);
    read(m);
    int l, r;
    Rep(i, 1, m) {
        read(l);
        read(r);
        if (a[r] < l) a[r] = l;
    }

    int ans = 0, cut = a[1];
    Rep(i, 1, n) if (a[i]) {
        if (a[i] >= cut) {
            ans++;
            cut = i;
        }
    }
    pr(ans);
    return 0;
}

D XOR序列