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【BZOJ 2351】Matrix（Hash）
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題目鏈接
二維\(Hash\)類似二維前綴和，每一行看成一個\(h\)進制數，每一個以(1,1)為左上角的矩陣看成一個由每一行的\(Hash\)值組成的\(l\)進制數。
然后自己推推柿子就行。
#include <cstdio>
#include <cstring>
#include <map>
using namespace std;
#define Open(s) freopen(s".in","r",stdin); freopen(s".out","w",stdout);
#define h 1331
#define l 2333
int n, m, r, c, T;
map <unsigned long long, int> mp;
unsigned long long hs[1010][1010], ph[1010], pl[1010], xs[1010][1010];
char ch;
int main(){Open("matrix"); ph[0] = pl[0] = 1;scanf("%d%d%d%d", &n, &m, &r, &c);for(int i = 1; i <= n; ++i)for(int j = 1; j <= m; ++j){ch = getchar();while(ch != '0' && ch != '1') ch = getchar();hs[i][j] = hs[i][j - 1] * h + ch;}for(int i = 1; i <= n; ++i)for(int j = 1; j <= m; ++j)hs[i][j] += hs[i - 1][j] * l;for(int i = 1; i <= m; ++i) ph[i] = ph[i - 1] * h;for(int i = 1; i <= n; ++i) pl[i] = pl[i - 1] * l; for(int i = r; i <= n; ++i)for(int j = c; j <= m; ++j)mp[hs[i][j] - hs[i - r][j] * pl[r] - hs[i][j - c] * ph[c] + hs[i - r][j - c] * pl[r] * ph[c]] = 1;scanf("%d", &T);while(T--){for(int i = 1; i <= r; ++i)for(int j = 1; j <= c; ++j)xs[i][j] = 0;for(int i = 1; i <= r; ++i)for(int j = 1; j <= c; ++j){ch = getchar();while(ch != '0' && ch != '1') ch = getchar();xs[i][j] = xs[i][j - 1] * h + ch;}for(int i = 1; i <= r; ++i)for(int j = 1; j <= c; ++j)xs[i][j] += xs[i - 1][j] * l;printf("%d\n", mp[xs[r][c]]);}return 0;
}
轉載于:https://www.cnblogs.com/Qihoo360/p/11224239.html
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