USACO:Number Triangles

最简单的dp

/*
ID: Jang Lawrence
PROG: numtri
LANG: C++
*/
#include<iostream>
#include<cstring>
#include<cstdio>
#include<algorithm>
#include<queue>
using namespace std;
int Max(int x,int y){if(x<y) return y;return x;}
int n;
int a[1001][1001],dp[1001][1001];
int main()
{
    #ifndef  DEBUG
  freopen("numtri.in","r",stdin);
  freopen("numtri.out","w",stdout);
  #endif
   scanf("%d",&n);
   for(int i=0;i<n;++i)
   for(int j=0;j<=i;++j)
   scanf("%d",&a[i][j]);
   dp[0][0]=a[0][0];
   for(int i=1;i<n;++i)
   {
       dp[i][0]=dp[i-1][0]+a[i][0];
       for(int j=1;j<i;++j)
       dp[i][j]=Max(dp[i-1][j-1],dp[i-1][j])+a[i][j];
       dp[i][i]=dp[i-1][i-1]+a[i][i];
   }
   int ans=0;
   for(int i=0;i<n;++i)
   ans=Max(ans,dp[n-1][i]);
   printf("%d\n",ans);
    return 0;
}