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Cod sursa(job #705372)
#include <cstring>
#include <cstdlib>
#include <cstdio>
#include <cmath>
int n, m, s;
struct Con {
int b, a;
};
bool vis[100008];
Con con[1000008];
int idx[100008];
int nxt[100008];
int dpt[100008];
int compare(const void * a, const void * b) {
return(((Con *)a)->a - ((Con *)b)->a);
}
int main() {
FILE * in = fopen("bfs.in", "rt");
FILE * out = fopen("bfs.out", "wt");
fscanf(in, "%d%d%d", &n, &m, &s);
for (int i = 0; i < m; ++i) {
fscanf(in, "%d%d", &con[i].a, &con[i].b);
if (con[i].a == con[i].b) {
--i;
--m;
}
}
qsort(con, m, sizeof(Con), compare);
int k = 0;
for (int i = 0; i < m; ++i) {
if (k != con[i].a) {
k = con[i].a;
idx[k] = i;
}
}
for (int i = 1; i <= n; ++i) {
dpt[i] = -1;
}
int l = 0, r = 0;
nxt[r++] = s;
vis[s] = 1;
dpt[s] = 0;
while (l <= r) {
int ta = nxt[l];
for (int i = idx[ta]; con[i].a == ta; ++i) {
int tb = con[i].b;
if (!vis[tb]) {
vis[tb] = 1;
nxt[r++] = tb;
dpt[tb] = dpt[ta] + 1;
}
}
++l;
}
for (int i = 1; i <= n; ++i) {
fprintf(out, "%d ", dpt[i]);
}
fclose(in);
fclose(out);
}