专题四 · 1010

来源：互联网发布：行情软件破解编辑：程序博客网时间：2024/05/29 01:51
代码及解释

#include <stdio.h>#include <iostream>#include <queue>// 最短路之后深搜// 用的队列优化////typedef struct n1 { int distens, flog; } node;node N[1005];int map[1005][1005], k;int direct[1005];void set(int n) {  int i, j, m, n1, n2, d;  for (i = 1; i <= n; i++) {    for (j = 1; j <= n; j++) {      map[i][j] = -1;    }    N[i].distens = 10000000;    N[i].flog = 0;    direct[i] = 0;  }  scanf("%d", &m);  while (m--) {    scanf("%d%d%d", &n1, &n2, &d);    if (map[n1][n2] != 0 || map[n1][n2] > d)      map[n1][n2] = map[n2][n1] = d;  }}void spfa(int n) {  std::queue<int> Q;  int now;  int i;  N[2].distens = 0;  N[2].flog = 1;  Q.push(2);  while (!Q.empty()) {    now = Q.front();    Q.pop();    N[now].flog = 0;    for (i = 1; i <= n; i++)      if (map[now][i] != -1) {        if (N[i].distens > N[now].distens + map[now][i]) {          N[i].distens = N[now].distens + map[now][i];          if (N[i].flog == 0) {            N[i].flog = 1;            Q.push(i);          }        }      }  }}int DFS(int now, int n) {  int i;  if (direct[now] > 0)    return direct[now];  if (now == 2) {    return 1;  }  for (i = 1; i <= n; i++)    if (map[now][i] != -1 && N[now].distens > N[i].distens)      direct[now] += DFS(i, n);  return direct[now];}int main() {  int n;  while (scanf("%d", &n) > 0 && n) {    set(n);    spfa(n);    k = DFS(1, n);    printf("%d\n", k);  }}
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