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41 lines
908 B
C++
41 lines
908 B
C++
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#include <bits/stdc++.h>
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using namespace std;
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int n, m, a, b, f[105][105], ans[105];
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int main() {
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cin >> n >> m;
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for (int i = 1; i <= n; i++) {
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for (int j = 1; j <= n; j++) {
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f[i][j] = i == j ? 0 : 0x3f3f3f3f;
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}
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}
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for (int i = 1; i <= m; i++) {
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cin >> a >> b;
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f[a][b] = 1;
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}
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for (int k = 1; k <= n; k++) {
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for (int i = 1; i <= n; i++) {
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for (int j = 1; j <= n; j++) {
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f[i][j] = min(f[i][j], f[i][k] + f[k][j]);
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}
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}
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}
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for (int i = 1; i <= n; i++) {
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for (int j = 1; j <= n; j++) {
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if (f[i][j] != 0x3f3f3f3f && f[i][j] > 0) {
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ans[i]++;
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ans[j]++;
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}
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}
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}
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for (int i = 1; i <= n; i++) {
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if (ans[i] == n - 1) {
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ans[0]++;
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}
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}
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cout << ans[0] << endl;
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return 0;
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}
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