diff --git a/src/algorithm.c b/src/algorithm.c
index ce05418..333c82d 100644
--- a/src/algorithm.c
+++ b/src/algorithm.c
@@ -758,6 +758,7 @@ void move_colle(creneau* edt, int len_edt, int id_src, int id_dest) {
 }
 
 void swap_colle(creneau* edt, int len_edt, int id_src, int id_dest) {
+    // BROKEN
     if((id_src < len_edt && id_dest < len_edt) == false) {
         printf("Bad\n");
         exit(1);
@@ -767,11 +768,11 @@ void swap_colle(creneau* edt, int len_edt, int id_src, int id_dest) {
     edt[id_dest].group = edt[id_src].group;
     
     //printf("%d %d\n", edt[id_src].group, dest_grp);
-    //edt[id_src].group = edt[id_src].group;
+    edt[id_src].group = edt[id_src].group;
 }
 
-int mem_id(creneau* edt, int len_edt, int grp, char* colleur) {
-    for(int i = 0; i < len_edt; i++) {
+int mem_id(creneau* edt, int len_edt, int grp, char* colleur, int offset) {
+    for(int i = offset; i < len_edt; i++) {
         if(edt[i].group == grp && str_equal(edt[i].name, colleur)) {
             return i;
         }
@@ -1146,6 +1147,147 @@ topic get_mat_from_id(colleur* dudes, int n_dudes, int id) {
     return NOTHING;
 }
 
+int** generate_matrix(int lines, int columns, int def) {
+    int** mat = malloc(sizeof(int*)*lines);
+    for(int i = 0; i < lines; i++) {
+        mat[i] = malloc(sizeof(int)*columns);
+        for(int j = 0; j < columns; j++) {
+            mat[i][j] = def;
+        }
+    }
+    return mat;
+}
+
+void destroy_matrix(int** m, int li) {
+    for(int i = 0; i < li; i++) {
+        free(m[i]);
+    }
+    free(m);
+}
+
+bool retreive_indexes(creneau* edt, int len_edt, int* p1, int* p2, int g1, int g2, char* n1, char* n2, int n_weeks) {
+    int* indexes_1 = malloc(sizeof(int)*n_weeks);
+    int* indexes_2 = malloc(sizeof(int)*n_weeks);
+    int ptr_1 = 0;
+    int ptr_2 = 0;
+
+    for(int i = 0; i < len_edt; i++) {
+        //printf("%d\n", i);
+        if(edt[i].group == g1 && str_equal(edt[i].name, n1)) {
+            indexes_1[ptr_1] = i;
+            ptr_1++;
+        } else if(edt[i].group == g2 && str_equal(edt[i].name, n2)) {
+            indexes_2[ptr_2] = i;
+            ptr_2++;
+        }
+    }
+
+    //print_arr(indexes_1, ptr_1);
+    //print_arr(indexes_2, ptr_2);
+
+    int j = 0;
+    for(int i = 0; i < ptr_1; i++) {
+        if(j >= ptr_2) {
+            free(indexes_1);
+            free(indexes_2);
+            return false;
+        } else {
+            //printf("{%d %d}\n", i, j);
+            int friday_1 = get_next_friday(edt, len_edt, edt[indexes_1[i]].date);
+            int friday_2 = get_next_friday(edt, len_edt, edt[indexes_2[j]].date);
+            if(friday_1 == friday_2) {
+                *p1 = indexes_1[i];
+                *p2 = indexes_2[j];
+
+                free(indexes_1);
+                free(indexes_2);
+                return true;
+            } else {
+                if(friday_1 > friday_2) {
+                    i--;
+                    j++;
+                }
+            }
+        }
+    }
+
+    free(indexes_1);
+    free(indexes_2);
+    return false;
+}
+
+void occurencies(creneau* edt, int len_edt, colleur* dudes, int n_groups, int n_colleurs, int n_weeks) {
+    //printf("{%d}\n", n_groups);
+    int max_occ = 1;
+    int** res = generate_matrix(n_groups, n_colleurs, 0);
+
+    for(int c = 0; c < len_edt; c++) {
+        if(edt[c].group != 0) {
+            res[edt[c].group-1][get_colleur_id(dudes, n_colleurs, edt[c].name)] += 1;
+        }
+    }
+
+    /*for(int k = 0; k < n_groups; k++) {
+        printf("Group %d : ", k+1);
+        print_arr(res[k], n_colleurs);
+    }
+    printf("\n");   // caused a minor panic  */
+
+    bool halt = false;
+    for(int it = 0; it < 3; it++) {
+        for(int grp = 0; grp < n_groups; grp++) {
+            for(int dud = 0; dud < n_colleurs; dud++) {
+                if(res[grp][dud] > max_occ) {
+                    for(int grp2 = 0; grp2 < n_groups*(1-halt); grp2++) {
+                        if(grp2 != grp) {
+                            for(int dud2 = 0; dud2 < n_colleurs*(1-halt); dud2++) {
+                                if(dud2 != dud && res[grp2][dud2] > max_occ && res[grp][dud2] < max_occ && res[grp2][dud] < max_occ && get_mat_from_id(dudes, n_colleurs, dud) == get_mat_from_id(dudes, n_colleurs, dud2)) {
+
+                                    int id_src;
+                                    int id_dest;
+                                    if(retreive_indexes(edt, len_edt, &id_src, &id_dest, grp+1, grp2+1, get_name_from_id(dudes, n_colleurs, dud), get_name_from_id(dudes, n_colleurs, dud2), n_weeks)) {;
+                                    // RESOLVED : both colles need to be the same week
+
+                                        if(id_src < 0 || id_dest < 0 || id_src >= len_edt || id_dest >= len_edt) {
+                                            printf("Uh oh (%d %d)\n", id_src, id_dest);
+                                            exit(1);
+                                        }
+
+                                        res[grp][dud] -= 1;
+                                        res[grp2][dud2] -= 1;
+                                        res[grp2][dud] += 1;
+                                        res[grp][dud2] += 1;
+
+                                        //printf("%d %d | ", edt[id_src].group, edt[id_dest].group);
+                                        edt[id_src].group += edt[id_dest].group;
+                                        edt[id_dest].group = edt[id_src].group - edt[id_dest].group;
+                                        edt[id_src].group -= edt[id_dest].group;
+                                        //printf("%d %d\n", edt[id_src].group, edt[id_dest].group);
+
+                                        //printf("[%d %d - %d] <==> [%d %d - %d]\n", grp+1, id_src, edt[id_src].group, grp2+1, id_dest, edt[id_dest].group);
+                                        halt = true;
+                                        dud--;
+                                    }
+                                }
+                            }
+                        }
+                    }
+                }
+                halt = false;
+            }
+        }
+    }
+
+    /*
+    for(int k = 0; k < n_groups; k++) {
+        printf("Group %d : ", k+1);
+        print_arr(res[k], n_colleurs);
+    }
+    printf("\n");*/
+
+    destroy_matrix(res, n_groups);
+}
+
 void aux_2(creneau* edt, int len_edt, colleur* chads, int len_chads, int n_groups, int n_weeks, int n_sim, char* outname) {
     int start = time(NULL);
     int* weeks_len = malloc(sizeof(int)*n_weeks);
@@ -1192,6 +1334,7 @@ void aux_2(creneau* edt, int len_edt, colleur* chads, int len_chads, int n_group
             //add_colles_for_group_MP2I(weeks_len, edt, len_edt, chads, len_chads, n_weeks, i+1, (topic)(2+i%2), i%4, i%6, &skipped);
             add_colles_for_group_MP2I(weeks_len, edt, len_edt, chads, len_chads, n_weeks, i+1, (topic)(2+i%2), i%3, -20, &skipped);
         }
+        occurencies(edt, len_edt, chads, n_groups, len_chads, n_weeks);
         for(int i = 0; i < n_groups; i++) {
             //printf("Score for group %d : %d\n", i+1, score(edt, len_edt, i+1));
             temp = score(edt, len_edt, i+1, n_weeks);
diff --git a/src/algorithm.h b/src/algorithm.h
index a79bc72..69dae0a 100644
--- a/src/algorithm.h
+++ b/src/algorithm.h
@@ -46,7 +46,7 @@ void move_colle(creneau* edt, int len_edt, int id_src, int id_dest);
 
 void swap_colle(creneau* edt, int len_edt, int id_src, int id_dest);
 
-int mem_id(creneau* edt, int len_edt, int grp, char* colleur);
+int mem_id(creneau* edt, int len_edt, int grp, char* colleur, int offset);
 
 bool is_overlap(creneau *edt, int len_edt, int id);
 
@@ -66,6 +66,14 @@ char* get_name_from_id(colleur* dudes, int n_dudes, int id);
 
 topic get_mat_from_id(colleur* dudes, int n_dudes, int id);
 
+int** generate_matrix(int lines, int columns, int def);
+
+void destroy_matrix(int** m, int li);
+
+bool retreive_indexes(creneau* edt, int len_edt, int* p1, int* p2, int g1, int g2, char* n1, char* n2, int n_weeks);
+
+void occurencies(creneau* edt, int len_edt, colleur* dudes, int n_groups, int n_colleurs, int n_weeks);
+
 void aux_2(creneau *edt, int len_edt, colleur *chads, int len_chads, int n_groups, int n_weeks, int n_sim, char *outname);
 
 #endif