three more codes

README.md

@@ -24,9 +24,9 @@ Chapter 4: 6/6
 
 Chapter 5: 11/12
 
-Chapter 6: 18/22
+Chapter 6: 20/22
 
-Chapter 7: 10/15
+Chapter 7: 11/15
 
 Chapter 8: 17/19
 

ch6/UVa1103.cpp

@@ -0,0 +1,121 @@
+// UVa1103 Ancient Messages
+// Rujia Liu
+// we pad one empty line/column to the top/bottom/left/right border, so color 1 is always "background" white
+#include<cstdio>
+#include<cstring>
+#include<algorithm>
+#include<vector>
+#include<set>
+using namespace std;
+
+char bin[256][5];
+
+const int maxh = 200 + 5;
+const int maxw = 50 * 4 + 5;
+
+int H, W, pic[maxh][maxw], color[maxh][maxw];
+char line[maxw];
+
+void decode(char ch, int row, int col) {
+  for(int i = 0; i < 4; i++)
+    pic[row][col+i] = bin[ch][i] - '0';
+}
+
+const int dr[] = {-1, 1, 0, 0};
+const int dc[] = {0, 0, -1, 1};
+
+// dfs from (row, col) and paint color c
+void dfs(int row, int col, int c) {
+  color[row][col] = c;
+  for(int i = 0; i < 4; i++) {
+    int row2 = row + dr[i];
+    int col2 = col + dc[i];
+    if(row2 >= 0 && row2 < H && col2 >= 0 && col2 < W && pic[row2][col2] == pic[row][col] && color[row2][col2] == 0)
+      dfs(row2, col2, c);
+  }
+}
+
+vector<set<int> > neighbors;
+
+void check_neighbors(int row, int col) {
+  for(int i = 0; i < 4; i++) {
+    int row2 = row + dr[i];
+    int col2 = col + dc[i];
+    if(row2 >= 0 && row2 < H && col2 >= 0&& col2 < W && pic[row2][col2] == 0 && color[row2][col2] != 1)
+      neighbors[color[row][col]].insert(color[row2][col2]);
+  }
+}
+
+const char* code = "WAKJSD";
+
+char recognize(int c) {
+  int cnt = neighbors[c].size();
+  return code[cnt];
+}
+
+// use this function to print the decoded picture
+void print() {
+  for(int i = 0; i < H; i++) {
+    for(int j = 0; j < W; j++) printf("%d", pic[i][j]);
+    printf("\n");
+  }
+}
+
+int main() {
+  strcpy(bin['0'], "0000");
+  strcpy(bin['1'], "0001");
+  strcpy(bin['2'], "0010");
+  strcpy(bin['3'], "0011");
+  strcpy(bin['4'], "0100");
+  strcpy(bin['5'], "0101");
+  strcpy(bin['6'], "0110");
+  strcpy(bin['7'], "0111");
+  strcpy(bin['8'], "1000");
+  strcpy(bin['9'], "1001");
+  strcpy(bin['a'], "1010");
+  strcpy(bin['b'], "1011");
+  strcpy(bin['c'], "1100");
+  strcpy(bin['d'], "1101");
+  strcpy(bin['e'], "1110");
+  strcpy(bin['f'], "1111");
+
+  int kase = 0;
+  while(scanf("%d%d", &H, &W) == 2 && H) {
+    memset(pic, 0, sizeof(pic));
+    for(int i = 0; i < H; i++) {
+      scanf("%s", line);
+      for(int j = 0; j < W; j++)
+        decode(line[j], i+1, j*4+1);
+    }
+
+    H += 2;
+    W = W * 4 + 2;
+
+    int cnt = 0;
+    vector<int> cc; // connected components of 1
+    memset(color, 0, sizeof(color));
+    for(int i = 0; i < H; i++)
+      for(int j = 0; j < W; j++)
+        if(!color[i][j]) {
+          dfs(i, j, ++cnt);
+          if(pic[i][j] == 1) cc.push_back(cnt);
+        }
+
+    neighbors.clear();
+    neighbors.resize(cnt+1);
+    for(int i = 0; i < H; i++)
+      for(int j = 0; j < W; j++)
+        if(pic[i][j] == 1)
+          check_neighbors(i, j);
+
+    vector<char> ans;
+    for(int i = 0; i < cc.size(); i++)
+      ans.push_back(recognize(cc[i]));
+    sort(ans.begin(), ans.end());
+
+    printf("Case %d: ", ++kase);
+    for(int i = 0; i < ans.size(); i++) printf("%c", ans[i]);
+    printf("\n");
+  }
+  return 0;
+}

ch6/UVa1599.cpp

@@ -0,0 +1,109 @@
+// UVa1599 Idea Path
+// Rujia Liu
+#include<cstdio>
+#include<cstring>
+#include<vector>
+#include<queue>
+using namespace std;
+
+const int maxn = 100000 + 5;
+const int INF = 1000000000; // maximal color
+
+struct Edge {
+  int u, v, c;
+  Edge(int u=0, int v=0, int c=0):u(u),v(v),c(c) {}
+};
+
+vector<Edge> edges;
+vector<int> G[maxn];
+
+void AddEdge(int u, int v, int c) {
+  edges.push_back(Edge(u, v, c));
+  int idx = edges.size() - 1;
+  G[u].push_back(idx);
+}
+
+int n, vis[maxn];
+int d[maxn];
+// reverse bfs to find out the distance from each node to n-1
+void rev_bfs() {
+  memset(vis, 0, sizeof(vis));
+  d[n-1] = 0;
+  vis[n-1] = true;
+
+  queue<int> q;
+  q.push(n-1);
+  while(!q.empty()) {
+    int v = q.front(); q.pop();
+    for(int i = 0; i < G[v].size(); i++) {
+      int e = G[v][i];
+      int u = edges[e].v;
+      if(!vis[u]) {
+        vis[u] = true;
+        d[u] = d[v] + 1;
+        q.push(u);
+      }
+    }
+  }
+}
+
+vector<int> ans;
+
+// forward bfs to construct the path
+void bfs() {
+  memset(vis, 0, sizeof(vis));
+  vis[0] = true;
+  ans.clear();
+
+  vector<int> next;
+  next.push_back(0);
+  for(int i = 0; i < d[0]; i++) {
+    int min_color = INF;
+    for(int j = 0; j < next.size(); j++) {
+      int u = next[j];
+      for(int k = 0; k < G[u].size(); k++) {
+        int e = G[u][k];
+        int v = edges[e].v;
+        if(d[u] == d[v] + 1)
+          min_color = min(min_color, edges[e].c);
+      }
+    }
+    ans.push_back(min_color);
+
+    // find out the next vertices of the next phase
+    vector<int> next2; 
+    for(int j = 0; j < next.size(); j++) {
+      int u = next[j];
+      for(int k = 0; k < G[u].size(); k++) {
+        int e = G[u][k];
+        int v = edges[e].v;
+        if(d[u] == d[v] + 1 && !vis[v] && edges[e].c == min_color) {
+          vis[v] = true;
+          next2.push_back(v);
+        }
+      }
+    }
+    next = next2;
+  }
+
+  printf("%d\n", ans.size());
+  printf("%d", ans[0]);
+  for(int i = 1; i < ans.size(); i++) printf(" %d", ans[i]);
+  printf("\n");
+}
+
+int main() {
+  int u, v, c, m;
+  while(scanf("%d%d", &n, &m) == 2) {
+    edges.size();
+    for(int i = 0; i < n; i++) G[i].clear();
+    while(m--) {
+      scanf("%d%d%d", &u, &v, &c);
+      AddEdge(u-1, v-1, c);
+      AddEdge(v-1, u-1, c);
+    }
+    rev_bfs();
+    bfs();
+  }
+  return 0;
+}

ch6/readme.md

@@ -30,7 +30,7 @@
 
 6-12 UVa572 Oil Deposits
 
-[暂缺]6-13 UVa1103 Ancient Messages
+6-13 UVa1103 Ancient Messages
 
 6-14 UVa816 Abbott's Revenge
 
@@ -44,7 +44,7 @@
 
 [暂缺]6-19 UVa1572 Self-Assembly
 
-[暂缺]6-20 UVa1599 Ideal Path
+6-20 UVa1599 Ideal Path
 
 6-21 UVa506 System Dependencies
 

ch7/UVa1343.cpp

@@ -0,0 +1,90 @@
+// UVa1343 The Rotation Game
+// Rujia Liu
+// This solutions uses IDA* instead of BFS described in the book, because it's shorter 8-)
+// It's shorter because no need for lookup tables and "automatically" lexicographically smallest solution.
+#include<cstdio>
+#include<algorithm>
+using namespace std;
+
+/*
+      00    01
+      02    03
+04 05 06 07 08 09 10
+      11    12
+13 14 15 16 17 18 19
+      20    21
+      22    23
+*/
+
+// lines E~H are computed with the help of rev[]
+int line[8][7]={
+  { 0, 2, 6,11,15,20,22}, // A
+  { 1, 3, 8,12,17,21,23}, // B
+  {10, 9, 8, 7, 6, 5, 4}, // C
+  {19,18,17,16,15,14,13}, // D
+};
+
+const int rev[8] = {5, 4, 7, 6, 1, 0, 3, 2}; // reverse lines of each line
+
+// center squares
+const int center[8] = {6, 7, 8, 11, 12, 15, 16, 17};
+
+int a[24];
+char ans[1000];
+
+bool is_final() {
+  for(int i = 0; i < 8; i++)
+    if (a[center[i]] != a[center[0]]) return false;
+  return true;
+}
+
+int diff(int target) {
+  int ans = 0;
+  for(int i = 0; i < 8; i++)
+    if(a[center[i]] != target) ans++;
+  return ans;
+}
+
+inline int h() {
+  return min(min(diff(1), diff(2)), diff(3));
+}
+
+inline void move(int i) {
+  int tmp = a[line[i][0]];
+  for(int j = 0; j < 6; j++) a[line[i][j]] = a[line[i][j+1]];
+  a[line[i][6]] = tmp;
+}
+
+bool dfs(int d, int maxd) {
+  if(is_final()) {
+    ans[d] = '\0';
+    printf("%s\n", ans);
+    return true;
+  }
+  if(d + h() > maxd) return false;
+  for(int i = 0; i < 8; i++) {
+    ans[d] = 'A' + i;
+    move(i);
+    if(dfs(d+1, maxd)) return true;
+    move(rev[i]);
+  }
+  return false;
+}
+
+int main() {
+  for(int i = 4; i < 8; i++)
+    for(int j = 0; j < 7; j++) line[i][j] = line[rev[i]][6-j];
+
+  while(scanf("%d", &a[0]) == 1 && a[0]) {
+    for(int i = 1; i < 24; i++) scanf("%d", &a[i]);
+    for(int i = 0; i < 24; i++) if(!a[i]) return 0;
+    if(is_final()) {
+      printf("No moves needed\n");
+    } else {
+      for(int maxd = 1; ; maxd++)
+        if(dfs(0, maxd)) break;
+    }
+    printf("%d\n", a[6]);
+  }
+  return 0;
+}

ch7/readme.md

@@ -60,7 +60,7 @@ egypt.cpp       - 埃及分数问题
 
 7-11 UVa12325 Zombie's Treasure Chest
 
-[暂缺]7-12 UVa1343 The Rotation Game
+7-12 UVa1343 The Rotation Game
 
 [暂缺]7-13 UVa1374 Power Calculus