UVA10054 The Necklace

深不可测的黑洞

呼~~终于把它A掉了

这道题是判断是否存在欧拉回路的，把颜色看成点，珍珠看成边，然后统计每一个点的度，如果有奇度就表明欧拉回路不存在，如果存在的话直接dfs出欧拉回路，然后扔到栈里最后直接输出就行了。（仰慕佳哥）

#include <cstdio>#include <cstring>#include <algorithm>#include <stack>#include <iostream>using namespace std;const int N = 55;int g[N][N], dg[N];stack<pair<int, int> >st;int is_euler(int mn){int s = -1;for (int i = 1; i <= mn; i++){if (dg[i]){if (s == -1) s = i;if (dg[i] % 2) return -1;}}return s;}void dfs(int cur, int mn){for (int i = 1; i <= mn; i++){if (g[cur][i]){g[cur][i] -= 1; g[i][cur] -= 1;dfs(i, mn);st.push(make_pair(cur, i));}}}int main(){    //freopen("out.txt", "w", stdout);int cs, n;scanf("%d", &cs);for (int p = 1; p <= cs; p++){    memset(g, 0, sizeof(g));    memset(dg, 0, sizeof(dg));if (p > 1) printf("\n");scanf("%d", &n);int x, y, mn = 0;for (int i = 0; i < n; i++){scanf("%d%d", &x, &y);g[x][y] += 1; g[y][x] += 1;dg[x] += 1; dg[y] += 1;mn = max(mn, max(x, y));}int f = is_euler(mn);printf("Case #%d\n", p);if (f == -1){puts("some beads may be lost");}else{dfs(f, mn);while(!st.empty()){printf("%d %d\n", st.top().first, st.top().second);st.pop();}}}return 0;}