Problem p02128 (C++)

Buggy submission (status: Time Limit Exceeded):
#include <bits/stdc++.h>
using namespace std;

typedef pair<int, int> P;

#define fi first
#define se second
#define repl(i, a, b) for (int i = (int)(a); i < (int)(b); i++)
#define rep(i, n) repl(i, 0, n)
#define all(x) (x).begin(), (x).end()
#define dbg(x) cout << #x "=" << x << endl
#define mmax(x, y) (x > y ? x : y)
#define mmin(x, y) (x < y ? x : y)
#define maxch(x, y) x = mmax(x, y)
#define minch(x, y) x = mmin(x, y)
#define uni(x) x.erase(unique(all(x)), x.end())
#define exist(x, y) (find(all(x), y) != x.end())
#define bcnt __builtin_popcount

#define INF INT_MAX / 3
#define mod 1000000007

struct state {
  int d;
  P p;
};
bool operator<(const state &a, const state &b) { return a.d > b.d; }

int w, h, n;
int x[101], y[101];
int dist[105][1001];

int main() {
  scanf("%d%d%d", &w, &h, &n);
  rep(i, n) scanf("%d%d", x + i, y + i);
  priority_queue<state> que;
  rep(i, n + 1) rep(j, w + h + 1) dist[i][j] = INF;
  que.push((state){0, P(n, 0)});
  int res = INF;
  while (que.size()) {
    P p = que.top().p;
    int d = que.top().d;
    que.pop();
    if (dist[p.fi][p.se] != INF)
      continue;
    dist[p.fi][p.se] = d;
    if (p.fi == n) { // start
      rep(i, n) {
        int md = abs(x[i] - 1) + abs(y[i] - 1);
        que.push((state){d + md, P(i, md)});
      }
    } else { // light
      rep(i, n) {
        int md = abs(x[i] - x[p.fi]) + abs(y[i] - y[p.fi]);
        if (md <= p.se + 1) {
          que.push((state){d, P(i, 0)});
        } else {
          md -= p.se + 1;
          que.push((state){d + md, P(i, md)});
        }
      }
      { // -> end
        int md = abs(x[p.fi] - w) + abs(y[p.fi] - h);
        if (md <= p.se) {
          minch(res, d);
        } else {
          md -= p.se;
          minch(res, d + md);
        }
      }
    }
  }
  cout << res << endl;
  return 0;
}


Fixed submission:
#include <bits/stdc++.h>
using namespace std;

typedef pair<int, int> P;

#define fi first
#define se second
#define repl(i, a, b) for (int i = (int)(a); i < (int)(b); i++)
#define rep(i, n) repl(i, 0, n)
#define all(x) (x).begin(), (x).end()
#define dbg(x) cout << #x "=" << x << endl
#define mmax(x, y) (x > y ? x : y)
#define mmin(x, y) (x < y ? x : y)
#define maxch(x, y) x = mmax(x, y)
#define minch(x, y) x = mmin(x, y)
#define uni(x) x.erase(unique(all(x)), x.end())
#define exist(x, y) (find(all(x), y) != x.end())
#define bcnt __builtin_popcount

#define INF INT_MAX / 3
#define mod 1000000007

struct state {
  int d;
  P p;
};
bool operator<(const state &a, const state &b) { return a.d > b.d; }

int w, h, n;
int x[101], y[101];
int dist[105][1001];

int main() {
  scanf("%d%d%d", &w, &h, &n);
  rep(i, n) scanf("%d%d", x + i, y + i);
  priority_queue<state> que;
  rep(i, n + 1) rep(j, w + h + 1) dist[i][j] = INF;
  que.push((state){0, P(n, 0)});
  int res = INF;
  while (que.size()) {
    P p = que.top().p;
    int d = que.top().d;
    que.pop();
    if (dist[p.fi][p.se] != INF)
      continue;
    dist[p.fi][p.se] = d;
    if (p.fi == n) { // start
      rep(i, n) {
        int md = abs(x[i] - 1) + abs(y[i] - 1);
        que.push((state){d + md, P(i, md)});
      }
    } else { // light
      rep(i, n) {
        if (x[i] < x[p.fi] && y[i] < y[p.fi])
          continue;
        if (i == p.fi)
          continue;
        int md = abs(x[i] - x[p.fi]) + abs(y[i] - y[p.fi]);
        if (md <= p.se + 1) {
          que.push((state){d, P(i, 0)});
        } else {
          md -= p.se + 1;
          que.push((state){d + md, P(i, md)});
        }
      }
      { // -> end
        int md = abs(x[p.fi] - w) + abs(y[p.fi] - h);
        if (md <= p.se) {
          minch(res, d);
        } else {
          md -= p.se;
          minch(res, d + md);
        }
      }
    }
  }
  cout << res << endl;
  return 0;
}