P1653

输出的答案有过大还有过小的，67pts，有3个点WA。

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

const int N = 510;
const int M = 1e6 + 10;
int n, m, H[N][N];
int cnt, head[N * N], ans1, ans2;
int low[N * N], dfn[N * N], scc, tot;
int in[N * N], out[N * N], id[N * N];
bool ins[N * N];
stack <int> st;

struct node {
	int from, to, next;
} e[M];

void add(int u, int v) {
	e[++ cnt] = {u, v, head[u]};
	head[u] = cnt;
}

void tarjan(int u) {
	dfn[u] = low[u] = ++ tot;
	ins[u] = u, st.push(u);
	for(int i = head[u]; i; i = e[i].next) {
		int v = e[i].to;
		if(!dfn[v]) {
			tarjan(v);
			low[u] = min(low[u], low[v]);
		}
		else if(ins[v]) low[u] = min(low[u], dfn[v]);
	}
	if(low[u] == dfn[u]) {
		int v = 0; scc ++;
		while(u != v) {
			v = st.top(), st.pop();
			ins[v] = 0, id[v] = scc;
		}
	}
}

inline int got(int h, int l) {
	return m * (h - 1) + l;
}

inline void R(int h, int l) {
	if(!H[h][l + 1]) return;
	int u = got(h, l + 1), v = got(h, l);
	if(H[h][l + 1] > H[h][l]) add(u, v);
	if(H[h][l + 1] == H[h][l]) add(u, v), add(v, u);
}

inline void D(int h, int l) {
	if(!H[h - 1][l]) return;
	int u = got(h, l), v = got(h - 1, l);
	if(H[h][l] > H[h - 1][l]) add(u, v);
	if(H[h][l] == H[h - 1][l]) add(u, v), add(v, u);
}

inline void solve() {
	for(int i = 1; i <= n; i ++) {
		for(int j = 1; j <= m; j ++) {
			D(i, j), R(i, j);
		}
	}
}

inline int rd() {
	int w = 1, x = 0;
	char c = getchar();
	while(c < 48 || c > 57) {
		if(c == 45) w *= -1;
		c = getchar();
	}
	while(c >= 48 && c <= 57) {
		x = (x << 1) + (x << 3) + (c ^ 48);
		c = getchar();
	}
	return x * w;
}

int main() {
	m = rd(), n = rd();
	for(int i = 1; i <= n; i ++) {
		for(int j = 1; j <= m; j ++) {
			H[i][j] = rd(); 
		}
	}
	solve();
	for(int i = 1; i <= n * m; i ++) {
		if(!dfn[i]) tarjan(i);
	}
	if(scc == 1) {
		cout << "0";
		return 0;
	}
	for(int i = 1; i <= cnt; i ++) {
		int u = e[i].from, v = e[i].to;
		if(id[u] == id[v]) continue;
		in[id[v]] ++, out[id[u]] ++;
	}
	for(int i = 1; i <= scc; i ++) {
		if(in[i] == 0) ans1 ++;
		if(out[i] == 0) ans2 ++;
	}
	printf("%d", max(ans1, ans2));
	return 0;
}