POJ 2353 DP

双向DP+记录路径。

// by SiriusRen
#include <stack>
#include <cstdio>
#include <cstring>
using namespace std;
stack<int>s;
int n,m,RECL,RECR,minn=0x3fffffff,a[555][555],f[555][555],recl[555][555],recr[555][555];
int main(){
    memset(f,0x3f,sizeof(f));
    scanf("%d%d",&n,&m);
    for(int i=1;i<=n;i++)for(int j=1;j<=m;j++)scanf("%d",&a[i][j]);
    for(int i=1;i<=m;i++)f[1][i]=a[1][i];
    for(int i=1;i<=n;i++){
        for(int j=1;j<m;j++)if(f[i][j]+a[i][j+1]<f[i][j+1])f[i][j+1]=f[i][j]+a[i][j+1],recl[i][j+1]=j,recr[i][j+1]=i;
        for(int j=m;j>1;j--)if(f[i][j]+a[i][j-1]<f[i][j-1])f[i][j-1]=f[i][j]+a[i][j-1],recl[i][j-1]=j,recr[i][j-1]=i;
        for(int j=1;j<=m;j++)f[i+1][j]=f[i][j]+a[i+1][j],recl[i+1][j]=j,recr[i+1][j]=i;
    }
    for(int i=1;i<=m;i++)if(minn>f[n][i])minn=f[n][i],RECL=i;
    RECR=n;
    while(RECR){
        s.push(RECL);
        int temp=recr[RECR][RECL];
        RECL=recl[RECR][RECL];
        RECR=temp;
    }
    while(!s.empty())printf("%d
",s.top()),s.pop();
}