【HDOJ】2155 小黑的镇魂曲
线段树+SPFA最短路可以过。或者DP也能过。
需要注意的是xl的范围是错的，测试用例中xl可能为0，他妈的，因为这个一直莫名其妙的wa。
1. spfa建图增加一倍的点即可（讨论左端点和右端点）。
1 /* 2155 */ 2 #include <iostream> 3 #include <sstream> 4 #include <string> 5 #include <map> 6 #include <queue> 7 #include <set> 8 #include <stack> 9 #include <vector> 10 #include <deque> 11 #include <algorithm> 12 #include <cstdio> 13 #include <cmath> 14 #include <ctime> 15 #include <cstring> 16 #include <climits> 17 #include <cctype> 18 #include <cassert> 19 #include <functional> 20 #include <iterator> 21 #include <iomanip> 22 using namespace std; 23 //#pragma comment(linker,"/STACK:102400000,1024000") 24 25 #define sti set<int> 26 #define stpii set<pair<int, int> > 27 #define mpii map<int,int> 28 #define vi vector<int> 29 #define pii pair<int,int> 30 #define vpii vector<pair<int,int> > 31 #define rep(i, a, n) for (int i=a;i<n;++i) 32 #define per(i, a, n) for (int i=n-1;i>=a;--i) 33 #define clr clear 34 #define pb push_back 35 #define mp make_pair 36 #define fir first 37 #define sec second 38 #define all(x) (x).begin(),(x).end() 39 #define SZ(x) ((int)(x).size()) 40 #define lson l, mid, rt<<1 41 #define rson mid+1, r, rt<<1|1 42 43 typedef struct { 44 int v, w, nxt; 45 } edge_t; 46 47 typedef struct node_t { 48 int xl, xr, y; 49 50 node_t() {} 51 node_t(int xl, int xr, int y): 52 xl(xl), xr(xr), y(y) {} 53 54 friend bool operator <(const node_t& a, const node_t& b) { 55 return a.y < b.y; 56 } 57 58 } node_t; 59 60 const int maxv = 1025; 61 const int maxe = maxv * 1000; 62 const int INF = 0x3f3f3f3f; 63 int n, x, y, mx, T; 64 edge_t E[maxe]; 65 int head[maxv<<1]; 66 bool visit[maxv<<1]; 67 int dis[maxv<<1]; 68 node_t nd[maxv]; 69 int l = 0, m; 70 int start, End; 71 int ID[maxv<<2]; 72 int L, R, id; 73 74 void init() { 75 l = 0; 76 m = 1; 77 memset(head, -1, sizeof(head)); 78 } 79 80 void addEdge(int u, int v, int w) { 81 E[l].v = v; 82 E[l].w = w; 83 E[l].nxt = head[u]; 84 head[u] = l++; 85 } 86 87 void Build(int l, int r, int rt) { 88 ID[rt] = 0; 89 if (l == r) 90 return ; 91 92 int mid = (l + r) >> 1; 93 Build(lson); 94 Build(rson); 95 } 96 97 inline void PushDown(int rt) { 98 if (ID[rt]) { 99 ID[rt<<1] = ID[rt<<1|1] = ID[rt]; 100 ID[rt] = 0; 101 } 102 } 103 104 void Update(int l, int r, int rt) { 105 if (L<=l && R>=r) { 106 ID[rt] = id; 107 return ; 108 } 109 110 PushDown(rt); 111 int mid = (l + r) >> 1; 112 113 if (R <= mid) { 114 Update(lson); 115 } else if (L > mid) { 116 Update(rson); 117 } else { 118 Update(lson); 119 Update(rson); 120 } 121 } 122 123 int Query(int k, int l, int r, int rt) { 124 if (l == r) 125 return ID[rt]; 126 127 PushDown(rt); 128 int mid = (l + r) >> 1; 129 130 if (k <= mid) 131 return Query(k, lson); 132 else 133 return Query(k, rson); 134 } 135 136 int spfa() { 137 queue<int> Q; 138 int u, v, k; 139 140 memset(visit, false, sizeof(visit)); 141 memset(dis, INF, sizeof(dis)); 142 dis[start] = 0; 143 visit[start] = true; 144 Q.push(start); 145 146 while (!Q.empty()) { 147 u = Q.front(); 148 Q.pop(); 149 visit[u] = false; 150 for (k=head[u]; k!=-1; k=E[k].nxt) { 151 v = E[k].v; 152 if (dis[u]+E[k].w < dis[v]) { 153 dis[v] = dis[u] + E[k].w; 154 if (!visit[v]) { 155 visit[v] = true; 156 Q.push(v); 157 } 158 } 159 } 160 } 161 162 return dis[End]; 163 } 164 165 int main() { 166 ios::sync_with_stdio(false); 167 #ifndef ONLINE_JUDGE 168 freopen("data.in", "r", stdin); 169 freopen("data.out", "w", stdout); 170 #endif 171 172 int t; 173 int lid, rid; 174 int tmp, w; 175 176 scanf("%d", &t); 177 rep(tt, 1, t+1) { 178 scanf("%d %d %d %d %d", &n, &x, &y, &mx, &T); 179 ++x; 180 init(); 181 rep(i, 0, n) { 182 scanf("%d %d %d", &nd[m].xl, &nd[m].xr, &nd[m].y); 183 ++nd[m].xl; 184 ++nd[m].xr; 185 if (nd[m].y < y) 186 ++m; 187 } 188 189 nd[m].xl = x; 190 nd[m].xr = x; 191 nd[m].y = y; 192 ++m; 193 nd[m].xl = 1; 194 nd[m].xr = 1002; 195 nd[m].y = 0; 196 sort(nd+1, nd+1+m); 197 End = 1; 198 start = m; 199 memset(ID, 0, sizeof(ID)); 200 201 L = nd[1].xl; 202 R = nd[1].xr; 203 id = 1; 204 Update(1, 1005, 1); 205 rep(i, 2, m+1) { 206 207 // handle left 208 L = nd[i].xl; 209 lid = Query(L, 1, 1005, 1); 210 tmp = nd[i].y - nd[lid].y; 211 if (tmp <= mx) { 212 if (lid == End) { 213 w = tmp; 214 addEdge(i, lid, w); 215 } else { 216 // to left of lid 217 w = tmp + nd[i].xl - nd[lid].xl; 218 addEdge(i, lid, w); 219 220 // to right of lid 221 w = tmp + nd[lid].xr - nd[i].xl; 222 addEdge(i, lid+m, w); 223 } 224 } 225 226 // handle right 227 if (i != m) { 228 R = nd[i].xr; 229 rid = Query(R, 1, 1005, 1); 230 tmp = nd[i].y - nd[rid].y; 231 if (tmp <= mx) { 232 if (rid == End) { 233 w = tmp; 234 addEdge(i+m, rid, w); 235 } else { 236 // to left of rid 237 w = tmp + nd[i].xr - nd[rid].xl; 238 addEdge(i+m, rid, w); 239 240 // to right of rid 241 w = tmp + nd[rid].xr - nd[i].xr; 242 addEdge(i+m, rid+m, w); 243 } 244 } 245 } 246 247 L = nd[i].xl; 248 R = nd[i].xr; 249 id = i; 250 251 Update(1, 1005, 1); 252 } 253 254 tmp = spfa(); 255 if (tmp==INF || tmp>T) 256 puts("YES"); 257 else 258 puts("NO"); 259 } 260 261 #ifndef ONLINE_JUDGE 262 printf("time = %d.\n", (int)clock()); 263 #endif 264 265 return 0; 266 }
2. DP, 二维DP，没什么好说的。
1 /* 2155 */ 2 #include <iostream> 3 #include <sstream> 4 #include <string> 5 #include <map> 6 #include <queue> 7 #include <set> 8 #include <stack> 9 #include <vector> 10 #include <deque> 11 #include <algorithm> 12 #include <cstdio> 13 #include <cmath> 14 #include <ctime> 15 #include <cstring> 16 #include <climits> 17 #include <cctype> 18 #include <cassert> 19 #include <functional> 20 #include <iterator> 21 #include <iomanip> 22 using namespace std; 23 //#pragma comment(linker,"/STACK:102400000,1024000") 24 25 #define sti set<int> 26 #define stpii set<pair<int, int> > 27 #define mpii map<int,int> 28 #define vi vector<int> 29 #define pii pair<int,int> 30 #define vpii vector<pair<int,int> > 31 #define rep(i, a, n) for (int i=a;i<n;++i) 32 #define per(i, a, n) for (int i=n-1;i>=a;--i) 33 #define clr clear 34 #define pb push_back 35 #define mp make_pair 36 #define fir first 37 #define sec second 38 #define all(x) (x).begin(),(x).end() 39 #define SZ(x) ((int)(x).size()) 40 #define lson l, mid, rt<<1 41 #define rson mid+1, r, rt<<1|1 42 43 typedef struct node_t { 44 int l, r, h; 45 46 node_t() {} 47 node_t(int l, int r, int h): 48 l(l), r(r), h(h) {} 49 50 friend bool operator< (const node_t& a, const node_t& b) { 51 return a.h > b.h; 52 } 53 54 } node_t; 55 56 const int maxn = 1005; 57 const int INF = 0x3f3f3f3f; 58 node_t nd[maxn]; 59 int dp[maxn][2]; 60 int n, x, y, mx, T; 61 62 void solve() { 63 bool fl, fr; 64 int tmp; 65 66 memset(dp, INF, sizeof(dp)); 67 dp[0][0] = dp[0][1] = 0; 68 rep(i, 0, n) { 69 #ifndef ONLINE_JUDGE 70 printf("l = %d, r = %d, [0] = %d, [1] = %d\n", nd[i].l, nd[i].r, dp[i][0], dp[i][1]); 71 #endif 72 fl = fr = true; 73 rep(j, i+1, n+1) { 74 tmp = nd[i].h - nd[j].h; 75 if (tmp > mx) 76 break; 77 if (fl && nd[j].l<=nd[i].l && nd[i].l<=nd[j].r) { 78 fl = false; 79 if (j == n) { 80 dp[j][0] = min(dp[j][0], dp[i][0]+tmp); 81 dp[j][1] = min(dp[j][1], dp[i][0]+tmp); 82 } else { 83 dp[j][0] = min(dp[j][0], dp[i][0]+tmp+nd[i].l-nd[j].l); 84 dp[j][1] = min(dp[j][1], dp[i][0]+tmp+nd[j].r-nd[i].l); 85 } 86 } 87 if (fr && nd[j].l<=nd[i].r && nd[i].r<=nd[j].r) { 88 fr = false; 89 if (j == n) { 90 dp[j][0] = min(dp[j][0], dp[i][1]+tmp); 91 dp[j][1] = min(dp[j][1], dp[i][1]+tmp); 92 } else { 93 dp[j][0] = min(dp[j][0], dp[i][1]+tmp+nd[i].r-nd[j].l); 94 dp[j][1] = min(dp[j][1], dp[i][1]+tmp+nd[j].r-nd[i].r); 95 } 96 } 97 } 98 } 99 100 if (dp[n][0]<=T || dp[n][1]<=T) 101 puts("NO"); 102 else 103 puts("YES"); 104 } 105 106 int main() { 107 ios::sync_with_stdio(false); 108 #ifndef ONLINE_JUDGE 109 freopen("data.in", "r", stdin); 110 freopen("data.out", "w", stdout); 111 #endif 112 113 int t; 114 115 scanf("%d", &t); 116 while (t--) { 117 scanf("%d %d %d %d %d", &n, &x, &y, &mx, &T); 118 nd[0].l = nd[0].r = x; 119 nd[0].h = y; 120 rep(i, 1, n+1) 121 scanf("%d %d %d", &nd[i].l, &nd[i].r, &nd[i].h); 122 sort(nd, nd+n); 123 ++n; 124 nd[n].l = 0; 125 nd[n].r = 1010; 126 nd[n].h = 0; 127 solve(); 128 } 129 130 #ifndef ONLINE_JUDGE 131 printf("time = %d.\n", (int)clock()); 132 #endif 133 134 return 0; 135 }
