HDU3359 Kind of a Blur(高斯消元)

Posted 2020-08-12

建立方程后消元

 

#include<cstdio>
#include<iostream>
#include<cstdlib>
#include<cstring>
#include<string>
#include<algorithm>
#include<map>
#include<queue>
#include<vector>
#include<cmath>
#include<utility>
using namespace std;
typedef long long LL;
const int N = 108, INF = 0x3F3F3F3F;
const double eps = 1e-8;
double f[N][N];
bool inf[N];

template<typename T>
void gauss_jordan(T A[N][N], int n){
    for(int i = 0; i < n; i++){
        //选择一行r与第i行交换
        int r = i;
        for(int j = i + 1; j < n; j++){
            if(abs(A[j][i]) > abs(A[r][i])){
                r = j;
            }
        }
        if(abs(A[r][i]) < eps){
            continue;
        }
        if(r != i){
            for(int j = 0; j <= n; j++){
                swap(A[r][j], A[i][j]);
            }
        }
        for(int k = 0; k < n; k++){
            if(k != i){
                for(int j = n; j >= i; j--){
                    A[k][j] -=  A[k][i] / A[i][i] * A[i][j];
                }
            }
        }
    }
}

int main(){
    bool flag = 0;
    int h, w, d;
    while(scanf("%d %d %d", &w, &h, &d), w || h || d){
        memset(f, 0, sizeof(f));
        for(int i = 0; i < h; i++){
            for(int j = 0; j < w; j++){
                double t;
                scanf("%lf", &t);
                int u = i * w + j;
                f[u][w * h] = t;
                int cnt = 0;
                for(int x = max(0, i - d) ; x <= min(h - 1, i + d); x++){
                    for(int y = max(0, j - d) ; y <= min(w - 1, j + d); y++){
                        if(abs(x - i) + abs(y - j) <= d){
                            cnt ++;
                        }
                    }
                }

                for(int x = max(0, i - d) ; x <= min(h - 1, i + d); x++){
                    for(int y = max(0, j - d) ; y <= min(w - 1, j + d); y++){
                        if(abs(x - i) + abs(y - j) <= d){
                            int v = x * w + y;
                            f[u][v] = 1.0 / (double)cnt;
                        }
                    }
                }
            }
        }
        gauss_jordan(f, w * h);
        if(flag){
            printf("\n");
        }
        flag = 1;
        for(int i = 0; i < h; i++){
            for(int j = 0; j < w; j++){
                printf("%8.2f", f[i * w + j][w * h] / f[i * w + j][i * w + j]);
            }
            printf("\n");
        }

    }
    return 0;
}