POJ_3414_BFS pots

/* * POJ_3414_BFS * I really like this bfs problem * On the first and only line are the numbers A, B, and C. These are all integers in the range from 1 to 100 and C≤max(A,B). */#include <iostream>#include <cstdio>#include <string>#include <cstring>#define BUG puts("here!!!");using namespace std;const int N = 205;struct Node {    int k1, k2;    int steps;    int op;    int pre;};bool vis[N][N];string str[10] = { "FILL(1)", "DROP(1)", "FILL(2)", "DROP(2)", "POUR(1,2)", "POUR(2,1)" }; Node cur, nex;Node que[N*N];int A, B, C;void dfs(Node pn) {    if (pn.pre != 0) {        dfs(que[pn.pre]);    }    cout << str[pn.op] << endl;}void bfs(int v1, int v2) {    cur.k1 = v1; cur.k2 = v2; cur.steps = 0; cur.pre = 0;    que[0] = cur;    vis[0][0] = 1;    int head = 0, tail = 1;    while (head < tail) {        Node top = que[head++];        if (top.k1 == C || top.k2 == C) {            cout << top.steps << endl;            if (C != 0) dfs(top);            return;        }        int yi = 0;        for (int i = 0; i < 6; i++) {            switch(i) {                case 0 : nex.k1 = A; nex.k2 = top.k2; break;                case 1 : nex.k1 = 0; nex.k2 = top.k2; break;                case 2 : nex.k1 = top.k1; nex.k2 = B; break;                case 3 : nex.k2 = top.k1; nex.k2 = 0; break;                case 4 :                     yi = top.k1 + top.k2 - B;                    if(yi > 0) nex.k1 = yi, nex.k2 = B;                    else nex.k1 = 0, nex.k2 = B + yi;                    break;                case 5 :                    yi = top.k1 + top.k2 - A;                    if(yi > 0) nex.k1 = A, nex.k2 = yi;                    else nex.k1 = A + yi, nex.k2 = 0;                    break;            }            nex.op = i;            nex.steps = top.steps + 1;            nex.pre = head - 1;            if (!vis[nex.k1][nex.k2]) {                que[tail++] = nex;                vis[nex.k1][nex.k2] = true;            }        }    }    printf("impossible\n");}int main() {    while (scanf("%d%d%d", &A, &B, &C) == 3) {        memset(vis, 0, sizeof(vis));        bfs(0, 0);    }    return 0;}