HDU 1428 漫步校园 SPFA + DFS记忆搜索
2013-01-29 10:20
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类似上题。
#include <stdio.h> #include <string.h> #define inf 0x7fffffff struct { int v, pow, next; }edge[52*52*4]; int n = 0, map[52][52], head[52*52], dis[52*52], dir[4][2] = {{-1, 0}, {0, -1}, {0, 1}, {1, 0}}; __int64 choise[52][52]; void init()//建图 { int i = 0, j = 0, k = 0, x = 0, y = 0, count = 0; memset(head, -1, sizeof(head)); for(i = 1; i<=n; i++) { for(j = 1; j<=n; j++) { for(k = 0; k<4; k++) { x = i+dir[k][0], y = j+dir[k][1]; if(x>0 && x<=n && y>0 && y<=n) { edge[count].pow = map[i][j]+map[x][y]; edge[count].v = (x-1)*n+y; edge[count].next = head[(i-1)*n+j]; //next域指向当前结点的前一条边,head指向最后一条边。邻接表表示 head[(i-1)*n+j] = count++; } } } } } void spfa() { int i = 0, p = 0, q = 0, row = 0, col = 0, front = 0, rear = 0, used[52*52], que[10000]; for(i = 1; i<=n*n; i++) { used[i] = 0; dis[i] = inf; } dis[n*n] = map ; used[n*n] = 1; que[rear++] = n*n; while(front != rear) { p = que[front]; row = p%n == 0? p/n:p/n+1;//求在原图中的位置 col = p%n == 0? n:p%n; front = (front+1)%10000; used[p] = 0; for(q = head[p]; q != -1; q = edge[q].next) { if(dis[edge[q].v]>dis[p]+edge[q].pow-map[row][col])//多出的要减去 { dis[edge[q].v] = dis[p]+edge[q].pow-map[row][col]; if(used[edge[q].v] == 0) { used[edge[q].v] = 1; que[rear] = edge[q].v; rear = (rear+1)%10000; } } } } } __int64 dfs(int x, int y)//记忆搜索 { int i = 0, fx = 0, fy = 0; if(choise[x][y]>0) return choise[x][y]; if(x == n && y == n) return 1; for(i = 0; i<4; i++) { fx = x+dir[i][0]; fy = y+dir[i][1]; if(fx>0 && fx<=n && fy>0 && fy<=n) { if(dis[(fx-1)*n+fy]<dis[(x-1)*n+y]) { choise[x][y] += dfs(fx, fy); } } } return choise[x][y]; } int main() { int i = 0, j = 0; while(scanf("%d",&n) != EOF) { for(i = 1; i<=n; i++) for(j = 1; j<=n; j++) scanf("%d",&map[i][j]); memset(choise, 0, sizeof(choise)); init(); spfa(); choise[1][1] = dfs(1, 1); printf("%I64d\n",choise[1][1]); } return 0; }
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