HDU 2485 Destroying the bus stations (IDA * + BFS)

Door: http://acm.hdu.edu.cn/showproblem.php? Pid = 1, 2485

Question: Give You n points, m edge, ask you to remove at least a few points to make the minimum path from 1 to n> = k, where 1 and n points cannot be removed.

Problem: this problem can be solved using the smallest stream or IDA * + BFS.

AC code:

# Include <iostream> # include <cstdio> # include <cstring> # include <string> # include <cstdlib> # include <cmath> # include <vector> # include <list> # include <deque> # include <queue> # include <iterator> # include <stack> # include <map> # include <set> # include <algorithm> # include <cctype> using namespace std; # define si1 (a) scanf ("% d", & a) # define I2 (a, B) scanf ("% d", & a, & B) # define sd1 (a) scanf ("% lf", & a) # define sd2 (a, B) Scanf ("% lf", & a, & B) # define ss1 (s) scanf ("% s", s) # define pi1 () printf ("% d \ n", a) # define pi2 (a, B) printf ("% d \ n", a, B) # define mset (, b) memset (a, B, sizeof (a) # define forb (I, a, B) for (int I = a; I <B; I ++) # define ford (I, a, B) for (int I = a; I <= B; I ++) typedef long LL; const int N = 1005; const int M = 105; const int INF = 0x3f3f3f3f; const double PI = acos (-1.0); const double eps = 1e-7; int n, m, k; int lin [N] [N]; // The list of adjacent tables stores the int Fa [N]; // record from 1 to n Shortest Path bool vis [N]; // mark whether the node is deleted int ans, Min; bool flag; struct xh {int x, y, next;} edge [N]; int bfs () {int q [2222]; int he = 0, ta = 0; mset (fa, -1); fa [1] = 0; mset (q, 0); q [ta ++] = 1; while (he! = Ta) {int x = q [he ++]; for (int I = 1; I <= lin [x] [0]; I ++) {int v = lin [x] [I]; if (fa [v] =-1 &&! Vis [v]) {fa [v] = x; q [ta ++] = v; if (n = v) return 1 ;}} return 0 ;} void dfs (int dian, int depth) // remove the minimum number point {if (flag = false) return; if (dian> depth) return; int p = bfs (); int sa [N] = {0}, t = 0; if (p = 0) {flag = false; return ;} for (int I = n; I! = 1; I = fa [I]) {sa [t ++] = I; if (t> k) {flag = false; return ;}} for (int I = 1; I <t; I ++) {int x = sa [I]; if (vis [x]) continue; vis [x] = 1; dfs (dian + 1, depth); vis [x] = 0; if (flag = false) return ;}} void IDA () {if (n <= 2) {puts ("0"); return;} int depth = 0; flag = true; vis [1] = 1; while (flag) {dfs (0, depth ); if (! Flag) break; depth ++;} pi1 (depth);} int main () {// freopen ("input.txt", "r", stdin ); while (scanf ("% d", & n, & m, & k) & (n + m + k) {mset (lin, 0 ); forb (I, 0, m) {int a, B, t; I2 (a, B); t = ++ lin [a] [0]; lin [a] [t] = B; // This place writes two-way WA, one-way A} IDA ();} return 0 ;}

Timeout Code: (IDA * + DFS) I think it should be similar, but it is time-out.

# Include <iostream> # include <cstdio> # include <cstring> # include <string> # include <cstdlib> # include <cmath> # include <vector> # include <list> # include <deque> # include <queue> # include <iterator> # include <stack> # include <map> # include <set> # include <algorithm> # include <cctype> using namespace std; # define si1 (a) scanf ("% d", & a) # define I2 (a, B) scanf ("% d", & a, & B) # define sd1 (a) scanf ("% lf", & a) # define sd2 (a, B) Scanf ("% lf", & a, & B) # define ss1 (s) scanf ("% s", s) # define pi1 () printf ("% d \ n", a) # define pi2 (a, B) printf ("% d \ n", a, B) # define mset (, b) memset (a, B, sizeof (a) # define forb (I, a, B) for (int I = a; I <B; I ++) # define ford (I, a, B) for (int I = a; I <= B; I ++) typedef long LL; const int N = 1005; const int M = 105; const int INF = 0x3f3f3f3f; const double PI = acos (-1.0); const double eps = 1e-7; int n, m, k; int lin [N] [N]; // The list of adjacent tables stores the int Cnt [M]; // record the Shortest Path bool vis [n] from 1 to N; // mark whether the node is deleted int ans, Min; bool flag; struct xh {int x, y, next;} edge [N]; void dfs2 (int k, int de) // calculate the shortest distance {cnt [de] = k; // path if (k = n) {Min = min (Min, de); return;} for (int I = 1; I <= lin [k] [0]; I ++) {int t = lin [k] [I]; if (vis [t]) continue; vis [t] = 1; dfs2 (t, de + 1); vis [t] = 0 ;}} void dfs1 (int dian, int depth) // remove the least number point {if (flag = false) return; Min = INF; mset (cnt, 0); dfs2 (); // cout <"shortest Distance from "<Min <endl; // cout <" Path: "; // if (Min! = INF) // {// for (int I = 0; I <= Min; I ++) // printf ("% d", cnt [I]); // cout <endl; //} // system ("pause"); int xh = Min; if (xh> = k) {flag = false; ans = min (ans, dian); return;} if (dian> = depth) return; int sa [N]; for (int I = 0; I <= xh; I ++) sa [I] = cnt [I]; for (int I = 1; I <xh; I ++) {int t = sa [I]; if (vis [t]) continue; vis [t] = 1; dfs1 (dian + 1, depth); vis [t] = 0; if (flag = false) return ;}} int main () {// freopen ("input.txt", "r", stdin); while (scanf ("% d", & n, & m, & k) & (n + m + k) {mset (lin, 0); forb (I, 0, m) {int a, B, t; i2 (a, B); t = ++ lin [a] [0]; lin [a] [t] = B; t = ++ lin [B] [0]; lin [B] [t] = a;} ans = INF; mset (vis, 0 ); vis [1] = 1; flag = true; int depth =-1; while (flag) {depth ++; dfs1 (0, depth);} pi1 (depth );} return 0 ;}