POJ-2531 network saboteur enumeration | randomization

Given a complete graph, we need to divide the graph into two parts and calculate the distance and maximum value of the points after the points of the two parts are cartesian products.

Solution 1: since a given number of points can be at most 20, you can simply enumerate the time complexity of 2 ^ N * O (n.

Solution 2: Use the randomization algorithm to enumerate a vertex and roll the set of the vertex.

The Code is as follows:

# Include <cstdlib> # include <cstring> # include <cstdio> # include <iostream> using namespace STD; int N, G [25] [25]; int Cal (int x) {int A [25], B [25], CA = 0, CB = 0, ret = 0; For (INT I = 0; I <n; ++ I) {If (X & (1 <I) {A [Ca ++] = I + 1 ;} else {B [CB ++] = I + 1 ;}} for (INT I = 0; I <CA; ++ I) {for (Int J = 0; j <CB; ++ J) {RET + = G [A [I] [B [J];} return ret;} int main () {int ret; while (scanf ("% d", & n) = 1) {ret = 0; For (INT I = 1; I <= N; ++ I) {for (Int J = 1; j <= N; ++ J) {scanf ("% d", & G [I] [J]) ;}} // store the specified information. Int mask = (1 <n)-1; for (INT I = 1; I <mask; ++ I) {ret = max (Ret, Cal (I);} printf ("% d \ n", RET);} return 0 ;}

The following randomization Code G ++ cannot be used. I don't know why.

# Include <cstdlib> # include <cstdio> # include <cstring> # include <iostream> # include <ctime> # include <map> using namespace STD; // The problem is relatively small. // The randomization algorithm can be used to solve the problem. Int N, G [30] [30]; int randtime = 200000; int A [30]; void moveatob (int x, Int & T) {A [x] = 0; For (INT I = 1; I <= N; ++ I) {if (a [I]) T + = G [x] [I]; else t-= G [x] [I] ;}} void movebtoa (INT X, int & T) {A [x] = 1; for (INT I = 1; I <= N; ++ I) {If (! A [I]) T + = G [x] [I]; else t-= G [x] [I] ;}} int randpro () {int Rd, ret = 0, T = 0; For (INT I = 0; I <randtime; ++ I) {RD = rand () % N + 1; // get a vertex, this point is indicated by if (a [RD]) {// description in the set moveatob (Rd, T);} else {// description in the B set movebtoa (Rd, t);} ret = max (Ret, T);} return ret;} int main () {srand (Time (null); While (scanf ("% d ", & n) = 1) {for (INT I = 1; I <= N; ++ I) {for (Int J = 1; j <= N; ++ J) {scanf ("% d", & G [I] [J]) ;}} for (INT I = 1; I <= N; ++ I) {A [I] = 1; // first assume that all elements belong to the first set} printf ("% d \ n", randpro ();} return 0 ;}