題目鏈接

bzoj3111: [Zjoi2013]螞蟻尋路

題解

發現走出來的圖是一向上的凸起鋸齒狀
對於每個突出的矩形dp一下就好了

代碼

/*
*/
#include<cstdio> 
#include<algorithm> 
const int maxn = 127; 
inline int read() { 
    int x = 0,f = 1; 
    char c = getchar(); 
    while(c < '0' || c > '9'){if(c == '-')f = -1;c = getchar();}  
    while(c <= '9' && c >= '0') x = x * 10 + c - '0',c = getchar(); 
    return x * f; 
}   
const int INF = 0x3f3f3f3f; 
const int rp  = 0x7fffffff; 
int n,m,k; 
int sum[maxn][maxn],a[maxn][maxn]; 
int g[maxn][25][maxn][2]; 
int dp[maxn][maxn][maxn]; 
int main() { 
    int ans = -0x3f3f3f3f; 
    n = read(),m = read(),k = read(); 
    k = k << 1 | 1; 
    for(int i = 1;i <= n;++ i) for(int j = 1;j <= m;++ j) a[i][j] = read(), sum[i][j] = sum[i - 1][j] + a[i][j]; 
    for(int i = 1;i <= k;++ i) for(int j = 1;j <= n;++ j) 
        g[0][i][j][0] = g[0][i][j][1] = dp[0][i][j] = -INF; 
    for(int i = 1;i <= n;++ i) for(int j = 1;j <= m;++ j) { 
        for(int p = 1;p <= k;++ p) { 
            for(int h = i;h;-- h) 
                dp[j][p][h] = std::max(dp[j - 1][p][h],g[j - 1][p - 1][h][p % 2]) - sum[h - 1][j] + sum[i][j]; 
            g[j][p][1][0] = -INF; 
            for(int h = 2;h <= i;++ h) 
                g[j][p][h][0] = std::max(dp[j][p][h - 1],g[j][p][h - 1][0]); 
            g[j][p][i][1] = -INF; 
            for(int h = i - 1;h;-- h) 
                g[j][p][h][1] = std::max(dp[j][p][h + 1],g[j][p][h + 1][1]); 
        } 
        ans = std::max(ans,std::max(dp[j][k][i],g[j][k][i][0]) ); 
    } 
    printf("%d\n",ans); 
    return 0; 
}  
 

bzoj3111: [Zjoi2013]螞蟻尋路