原題鏈接:
http://bailian.openjudge.cn/2016acm/02/
解題思路:
l(i,j)表示從點(i,j)出發的最長滑行長度。
一個點(i,j),如果周圍沒有比它低的點,l(i,j)=1
否則
l(i,j)等於(i,j)周圍四個點中比(i,j)低且l的值最大的+1
具體的來說
現將所以點按高度從小到大排序,l初始化爲1
然後按排序遍歷所有點 每遍歷一個點 更新其周圍比他高的點的l值
源代碼
#include<cstdio>
#include<cstring>
using namespace std;
struct mad{
int x;
int y;
int v;
};
mad f[10010];
void sort(int l,int r){
mad p;
int i = l;
int j = r;
int mid = f[(l+r)/2].v;
while(i<=j){
while(f[i].v<mid ) i++;
while(f[j].v>mid ) j--;
if (i<=j){
p = f[i];
f[i] = f[j];
f[j] = p;
i++;
j--;
}
}
if (i<r) sort(i,r);
if (l<j) sort(l,j);
}
int maxn(int x,int y){
if (x>y)
return x;
return y;
}
int main(){
int t = 0;
int r,c;
int maxx =0;
int a[200][200],l[200][200];
scanf("%d%d",&r,&c);
memset(a,-1,sizeof(a));
for (int i=1;i<=r;i++)
for (int j=1;j<=c;j++){
scanf("%d",&a[i][j]);
f[t].x =i;
f[t].y =j;
f[t].v =a[i][j];
t++;
}
t--;
sort(0,t);
for (int i=1;i<=r;i++)
for (int j=1;j<=c;j++)
l[i][j] = 1;
for (int i=0;i<=t;i++){
if (a[f[i].x][f[i].y]<a[f[i].x-1][f[i].y])
l[f[i].x-1][f[i].y] = maxn(l[f[i].x-1][f[i].y],l[f[i].x][f[i].y]+1);
if (a[f[i].x][f[i].y]<a[f[i].x+1][f[i].y])
l[f[i].x+1][f[i].y] = maxn(l[f[i].x+1][f[i].y],l[f[i].x][f[i].y]+1);
if (a[f[i].x][f[i].y]<a[f[i].x][f[i].y-1])
l[f[i].x][f[i].y-1] = maxn(l[f[i].x][f[i].y-1],l[f[i].x][f[i].y]+1);
if (a[f[i].x][f[i].y]<a[f[i].x][f[i].y+1])
l[f[i].x][f[i].y+1] = maxn(l[f[i].x][f[i].y+1],l[f[i].x][f[i].y]+1);
}
for (int i=1;i<=r;i++)
for (int j=1;j<=c;j++)
if (maxx < l[i][j])
maxx = l[i][j];
printf("%d\n",maxx);
return 0;
}