能將題目轉化為圖的色數問題就基本解決了

#include<iostream> #include<algorithm> #include<math.h> #include<string.h> #include<stdio.h> #include<string> #include<vector> #include<queue> #include<map> #include<sstream> #include<cassert> using namespace std; const int maxn = 15; const int maxm = 100 + 5; int n, m, u[maxm], v[maxm], G[maxn][maxn]; int ind[1 << maxn], d[1 << maxn], best[1 << maxn], label[maxn]; bool independent(int mask) {for (int i = 0; i < maxn; i++) if(mask&(1<<i)){for (int j = 0; j < maxn; j++)if (mask&(1 << j)) {if (i != j && G[i][j])return false;//有邊}}return true;//無邊 }int dp(int mask) {int &ans = d[mask];if (ans >= 0)return ans;if (mask == 0)return 0;ans = maxn + 1;for (int s = mask; s;s= (s - 1)&mask) {if (ind[s]) {int v = dp(mask^s) + 1;if (v < ans) {ans = v;best[mask] = s;}}}return ans; } void mark(int mask, int c) {for (int i = 0; i < maxn; i++)if ((1 << i)&mask) {label[i] = c;} } int main() {while (cin >> m) {memset(G, 0, sizeof(G));int useful = 0;for (int i = 0; i < m; i++) {char r1[9], r2[9];scanf("%s%s", r1, r2);u[i] = r1[0] - 'L'; v[i] = r2[0] - 'L';G[u[i]][v[i]] = 1;useful |= (1 << u[i]);useful |= (1 << v[i]);}memset(ind, 0, sizeof(ind));for (int s = useful; s; s = (s - 1)&useful) {if (independent(s))ind[s] = true;}memset(d, -1, sizeof(d));int ans = dp(useful);cout << ans - 2 << endl;//將每層都做標記int s = useful, k = 0;while (s) {mark(s,k++);s ^= best[s];}for (int i = 0; i < m; i++) {if (label[u[i]] < label[v[i]]) {swap(u[i], v[i]);}cout << u[i] + 'L' << " " << v[i] + 'L' << endl;}}return 0; }

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總結

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