CF321E Ciel and Gondolas

 

CF321E Ciel and Gondolas

链接

题解

本来想练WQS的

结果还是只会分治

#include<bits/stdc++.h>

using namespace std;

inline int read()
{
    int f = 1,x = 0;
    char ch;
    do
    {
        ch = getchar();
        if(ch == '-') f = -1;
    }while(ch < '0' || ch > '9');
    do
    {
        x = (x<<3) + (x<<1) + ch - '0';
        ch = getchar();
    }while(ch >= '0' && ch <= '9');
    return f*x;
}

const int MAXN = 4000 + 10;
const int MAXK = 800 + 10;

#define ll long long
#define re register

int n,k;
int a[MAXN][MAXN],sum[MAXN][MAXN];
ll dp[MAXK][MAXN];

inline ll calc(int l,int r)
{
    return sum[r][r] - sum[r][l-1] -sum[l-1][r] + sum[l-1][l-1];
}

inline void solve(int x,int L,int R,int l,int r)
{
    if(L>R||l>r) return;
    int mid = (l+r)>>1,d = 0;
    for(int i=L;i<=R&&i<mid;i++)
    {
        ll res = calc(i+1,mid);
        if(dp[x][mid] > dp[x-1][i] + res)
        {
            dp[x][mid] = dp[x-1][i] + res;
            d = i;
        }
    }
    solve(x,L,d,l,mid-1);solve(x,d,R,mid+1,r);
}

int main()
{
    n = read(),k = read();
    for(re int i=1;i<=n;i++) for(re int j=1;j<=n;j++) a[i][j] = read(),sum[i][j] = sum[i][j-1]+sum[i-1][j]-sum[i-1][j-1]+a[i][j];
    memset(dp,127,sizeof(dp));dp[0][0] = 0;
    for(int i=1;i<=k;i++) solve(i,0,n,1,n);
    printf("%lld
",dp[k][n]/2);
}