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41 lines
989 B
C++
41 lines
989 B
C++
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#include <bits/stdc++.h>
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using namespace std;
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int n, m, u, v, g[55][55];
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bool f[55][55][55];
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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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g[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 >> u >> v;
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g[u][v] = f[u][v][0] = 1;
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}
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for (int p = 1; p <= 32; p++) {
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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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if (f[i][k][p - 1] && f[k][j][p - 1]) {
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f[i][j][p] = true;
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g[i][j] = 1;
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}
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}
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}
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}
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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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g[i][j] = min(g[i][j], g[i][k] + g[k][j]);
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}
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}
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}
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cout << g[1][n] << endl;
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return 0;
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}
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