hdu 3339 In Action shortest path

First I use two dimesion dynamic programming algorithm,The answer is TLE,So I improve my algorithm to one dimesion and solve it.

The portal :http://acm.hdu.edu.cn/showproblem.php?pid=3339

#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <iostream>
#include <algorithm>
#include <map>
#include <queue>
#include <stack>
#include <set>

#define MAXN 105

using namespace std;

const int INF = 0x3f3f3f3f;

bool vis[MAXN];
int pre[MAXN];
int cost[MAXN][MAXN];
int lowcost[MAXN];
int power[MAXN];
int dp[MAXN*MAXN];

void Init(){
memset(vis,0,sizeof(vis));
memset(pre,-1,sizeof(pre));
memset(cost,0x3f,sizeof(cost));
memset(lowcost,0x3f,sizeof(lowcost));
}

void Dijkstra(int n,int beg){
lowcost[beg] = 0;
for(int j=0;j<n;j++){
int Min = INF;
int k = -1;
for(int i=0;i<n;i++){
if(!vis[i]&&lowcost[i]<Min){
Min = lowcost[i];
k = i;
}
}
if(k==-1)break;
vis[k] = true;
for(int i=0;i<n;i++){
if(!vis[i]&&lowcost[k]+cost[k][i]<lowcost[i]){
lowcost[i] = lowcost[k] + cost[k][i];
pre[i] = k;
}
}
}
}

void Input(){
int T;
scanf("%d",&T);
while(T--){
Init();
int n,m;
scanf("%d %d",&n,&m);
int tempa,tempb,tempr;
for(int i=0;i<m;i++){
scanf("%d %d %d",&tempa,&tempb,&tempr);
if(cost[tempa][tempb]>tempr){
cost[tempa][tempb] = tempr;
cost[tempb][tempa] = tempr;
}
}
Dijkstra(n+1,0);
int power_sum = 0;
for(int i=1;i<=n;i++){
scanf("%d",power+i);
power_sum += power[i];
}
int road_sum = 0;
for(int i=1;i<=n;i++){
if(lowcost[i]!=INF)
road_sum += lowcost[i];
}
memset(dp,0,sizeof(dp));
for(int i=1;i<=n;i++){
if(lowcost[i] == INF)continue;
for(int j=road_sum;j>=lowcost[i];j--){
dp[j] = max(dp[j],dp[j-lowcost[i]]+power[i]);
}
}
int ans = INF;
for(int i=0;i<=road_sum;i++){
if(dp[i]>power_sum/2){
ans = i;
break;
}
}
if(ans==INF){
puts("impossible");
}
else{
printf("%d\n",ans);
}
}
}

int main(void){
Input();
return 0;
}