Cod sursa(job #2209859)

Utilizator TooHappyMarchitan Teodor TooHappy Data 4 iunie 2018 22:13:02
Problema Algoritmul lui Gauss Scor 100
Compilator cpp Status done
Runda Arhiva educationala Marime 3.33 kb
#include <bits/stdc++.h>
using namespace std;
      
ifstream in("gauss.in");
ofstream out("gauss.out");

#define eps 0.0000001

vector< vector< double > > sist;
vector< double > solutii;

int main() {
    ios::sync_with_stdio(false); in.tie(0); out.tie(0);
    
    int n, m; in >> n >> m;

    sist.resize(n + 1, vector< double >(m + 2)); solutii.resize(m + 1);
    for(int i = 1; i <= n; ++i) {
        for(int j = 1; j <= m + 1; ++j) {
            in >> sist[i][j];
        }
    }

    int i = 1, j = 1, k;
    while(i <= n && j <= m) {
        for(k = i; k <= n; ++k) {
            if(sist[k][j] < -eps || sist[k][j] > eps) {
                break;
            }
        }

        if(k == n + 1) {
            ++j;
            continue;
        }
        
        if(k != i) {
            swap(sist[k], sist[i]);
        }

        for(int l = j + 1; l <= m + 1; ++l) {
            sist[i][l] = sist[i][l] / sist[i][j];
        }
        sist[i][j] = 1.0;

        for(int u = i + 1; u <= n; ++u) {
            for(int l = j + 1; l <= m + 1; ++l) {
                sist[u][l] -= sist[u][j] * sist[i][l];
            }
            sist[u][j] = 0;
        }

        ++i; ++j;
    }

    for(int i = n; i >= 1; --i) {
        for(int j = 1; j <= m + 1; ++j) {
            if(sist[i][j] < -eps || sist[i][j] > eps) {
                if(j == m + 1) {
                    out << "Imposibil\n";
                    exit(0);
                }

                solutii[j] = sist[i][m + 1];
                for(int k = j + 1; k <= m; ++k) {
                    solutii[j] -= solutii[k] * sist[i][k];
                }

                break;
            }
        }
    }

    for(int i = 1; i <= m; ++i) {
        out << fixed << setprecision(8) << solutii[i] << " ";
    }
    out << "\n";
    
    /*
    for(int i = 0; i < n; ++i) {
        bool goOn = false;

        if(sist[i][i] == 0.0) {
            for(int j = i + 1; j < n; ++j) {
                if(sist[j][i] == 0.0) {
                    continue;
                }

                swap(sist[i], sist[j]);
                break;
            }
            goOn = true;
        }

        if(goOn == true) {
            continue;
        }

        for(int j = i + 1; j < n; ++j) {
            if(sist[j][i] == 0.0) {
                continue;
            }

            double temp = sist[i][i] / sist[j][i];
            if(sist[i][i] *  sist[j][i] < 0) {
                temp = -temp;
            }

            for(int k = i; k < m + 1; ++k) {
                sist[j][k] = sist[i][k] + temp * sist[j][k];
            }
        }
    }
    
    bool imposibil = true;
    for(int j = 0; j < m && imposibil; ++j) {
        if(sist[n - 1][j] != 0.0) {
            imposibil = false;
        }
    }

    if(imposibil) {
        out << "Imposibil\n";
        exit(0);
    }

    // Ramane de scos necunoscutele de jos in sus.
    
    solutii[m - 1] = sist[n - 1][m] / sist[n - 1][m - 1];

    for(int i = n - 2; i >= 0; --i) {
        double sol = sist[i][m];
        for(int j = m - 1; j > i; --j) {
            sol = sol - sist[i][j] * solutii[j];
        }

        if(sist[i][i] != 0.0) {
            sol /= sist[i][i];
        }
        solutii[i] = sol;
    }

    for(int i = 0; i < m; ++i) {
        out << fixed << setprecision(8) << solutii[i] << " ";
    }
    out << "\n";
    */
    in.close(); out.close();
      
    return 0;
}