bfs.
1 #include <cstdio> 2 #include <cstring> 3 #include <cstdlib> 4 #include <queue> 5 #include <iostream> 6 #include <string> 7 using namespace std; 8 9 #define MAXN 1005 10 11 char ops[5] = "+-*%"; 12 bool visit[MAXN]; 13 int n, m, k; 14 string op; 15 16 typedef struct node_t { 17 int s, n; 18 string op; 19 node_t (int ss, int nn, string opp) { 20 s = ss; 21 n = nn; 22 op = opp; 23 } 24 } node_t; 25 26 int bfs() { 27 queue<node_t> Q; 28 int ns[4], tmp; 29 int nn = ((n+1)%k+k)%k; 30 int mk = m*k; 31 32 Q.push(node_t(0, n, "")); 33 memset(visit, false, sizeof(visit)); 34 visit[(n%k+k)%k] = true; 35 36 while(!Q.empty()) { 37 node_t nd = Q.front(); 38 Q.pop(); 39 // + 40 ns[0] = (nd.n + m)%mk; 41 // - 42 ns[1] = (nd.n - m)%mk; 43 // * 44 ns[2] = (nd.n * m)%mk; 45 // % 46 ns[3] = (nd.n % m+m)%m%mk; 47 for (int i=0; i<4; ++i) { 48 tmp = (ns[i]%k+k)%k; 49 if (tmp == nn) { 50 op = nd.op + ops[i]; 51 return nd.s+1; 52 } 53 if (!visit[tmp]) { 54 visit[tmp] = true; 55 Q.push(node_t(nd.s+1, ns[i], nd.op+ops[i])); 56 } 57 } 58 } 59 60 return 0; 61 } 62 63 int main() { 64 int ans; 65 66 #ifndef ONLINE_JUDGE 67 freopen("data.in", "r", stdin); 68 #endif 69 70 while (scanf("%d%d%d", &n, &k, &m)!=EOF && (n||m||k)) { 71 ans = bfs(); 72 printf("%d ", ans); 73 if (ans) 74 cout <<op<<endl; 75 } 76 77 return 0; 78 }