hdu 3339 In Action shortest path

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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 105using 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;}

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