bzoj 1047 单调队列

做4次单调队列优化DP。

 /**************************************************************
     Problem: 1047
     User: idy002
     Language: C++
     Result: Accepted
     Time:2088 ms
     Memory:16756 kb
 ****************************************************************/

 #include <cstdio>
 #define N 1010

 struct Pair {
     int i, j, v;
     Pair(){}
     Pair( int i, int j, int v ):i(i),j(j),v(v){}
 };

 int n, m, r, ans;
 int v[N][N], dp[N][N], dmin[N][N], dmax[N][N];
 Pair qu[N]; int bg, ed;

 int dodp() {
     //  min
     for( int i=; i<=n; i++ ) {
         bg=, ed=;
         for( int j=; j<=m; j++ ) {
             while( bg<=ed && qu[bg].j<j-r+ ) bg++;
             while( bg<=ed && qu[ed].v>v[i][j] ) ed--;
             qu[++ed] = Pair(i,j,v[i][j]);
             dp[i][j] = qu[bg].v;
         }
     }
     for( int j=; j<=m; j++ ) {
         bg=, ed=;
         for( int i=; i<=n; i++ ) {
             while( bg<=ed && qu[bg].i<i-r+ ) bg++;
             while( bg<=ed && qu[ed].v>dp[i][j] ) ed--;
             qu[++ed] = Pair(i,j,dp[i][j]);
             dmin[i][j] = qu[bg].v;
         }
     }
     //  max
     for( int i=; i<=n; i++ ) {
         bg=, ed=;
         for( int j=; j<=m; j++ ) {
             while( bg<=ed && qu[bg].j<j-r+ ) bg++;
             while( bg<=ed && qu[ed].v<v[i][j] ) ed--;
             qu[++ed] = Pair(i,j,v[i][j]);
             dp[i][j] = qu[bg].v;
         }
     }
     for( int j=; j<=m; j++ ) {
         bg=, ed=;
         for( int i=; i<=n; i++ ) {
             while( bg<=ed && qu[bg].i<i-r+ ) bg++;
             while( bg<=ed && qu[ed].v<dp[i][j] ) ed--;
             qu[++ed] = Pair(i,j,dp[i][j]);
             dmax[i][j] = qu[bg].v;
         }
     }
     int ans = ;
     for( int i=r; i<=n; i++ )
         for( int j=r; j<=m; j++ ) {
             int tans = dmax[i][j]-dmin[i][j];
             if( ans>tans ) ans=tans;
         }
     /*  debug
     fprintf( stderr, "n=%d m=%d r=%d\n", n, m, r );
     fprintf( stderr, "v:\n" );
     for( int i=1; i<=n; i++ ) {
         for( int j=1; j<=m; j++ )
             fprintf( stderr, "%2d ", v[i][j] );
         fprintf( stderr, "\n" );
     }
     fprintf( stderr, "dmin:\n" );
     for( int i=1; i<=n; i++ ) {
         for( int j=1; j<=m; j++ )
             fprintf( stderr, "%2d ", dmin[i][j] );
         fprintf( stderr, "\n" );
     }
     fprintf( stderr, "dmax:\n" );
     for( int i=1; i<=n; i++ ) {
         for( int j=1; j<=m; j++ )
             fprintf( stderr, "%2d ", dmax[i][j] );
         fprintf( stderr, "\n" );
     }
     */
     return ans;
 }
 int main() {
     scanf( "%d%d%d", &n, &m, &r );
     for( int i=; i<=n; i++ )
         for( int j=; j<=m; j++ )
             scanf( "%d", &v[i][j] );
     printf( "%d\n", dodp() );
 }