hdoj(hdu)-2813-KM+Trie

这个题做得我很郁闷,自己的KM模板照理说应该是没有问题,时间复杂度也是N^3,而N<201;一直超时,我在网上找代码也和我的代码差不多,我就相当的不理解为什么他们就可以过,而我的就是超时呢.后来我只得拿别人的代码一个一个地方改成我的代码的那个样子.发现改了很多地方还是可以过.只剩下输入没有改了,别人也是用MAP,我也是用MAP,我想应该是差不多吧,没想到是因为别人没有多次使用MAP查找,只查找了一次,而我是能用MAP的地方都用了,就这样导致我超时了.后来用字典树写了一下,竟然只要234MS就过了,而且还跑到了那个题的STATIC的第一.

 

总结:

1. 能够用字典树,还是尽量用字典树,虽然写起来用MAP要快,但是时间上MAP还是差很远的.一个是TLE,一个是AC ;

// 1005#include<cstdio>#include<cstdlib>#include<cmath>#include<cstring>#include<vector>#include<algorithm>#include<string>#include<map>#include<set>#include<stack>#include<bitset>#include<queue>#include<iostream>using namespace std;const int MaxN = 205;const int oo = 0x7f7f7f7f;int w[MaxN][MaxN];int lx[MaxN];int ly[MaxN];int linky[MaxN];int visx[MaxN];int visy[MaxN];int slack;int N;int M;bool find(int x){visx[x] = true;int y;for (y = 0; y < M; y++){if (visy[y] || w[x][y] == oo){continue;}int t = w[x][y] - lx[x] - ly[y];if (0 == t){visy[y] = true;if (linky[y] == -1 || find(linky[y])){linky[y] = x;return true;}}else if (slack > t){slack = t;}}return false;}int KM(){memset(linky, -1, sizeof(linky));memset(ly, 0, sizeof(ly));int i;int j;for (i = 0; i < N; i++){lx[i] = w[i][0];for (j = 1; j < M; j++){if (w[i][j] < lx[i]){lx[i] = w[i][j];}}}int x;for (x = 0; x < N; x++){while (1){memset(visx, 0, sizeof(visx));memset(visy, 0, sizeof(visy));slack = oo;if (find(x)){break;}for (i = 0; i < N; i++){if (visx[i]){lx[i] += slack;}}for (i = 0; i < M; i++){if (visy[i]){ly[i] -= slack;}}}}int ret = 0;for (i = 0; i < M; i++){if (linky[i] != -1){ret += w[linky[i]][i];}}return ret;}int nodecnt;int root;struct Dic{int next[256];int k;}node[10000];int NewNode(){memset(node[nodecnt].next, -1, sizeof(int)* 256);node[nodecnt].k = -1;return nodecnt++;}int dic_insert(char * s, int &cnt){int i;int x = root;for (i = 0; s[i]; i++){if (node[x].next[s[i]] == -1){node[x].next[s[i]] = NewNode();}x = node[x].next[s[i]];}if (node[x].k == -1){node[x].k = cnt++;}return node[x].k;}int main(){int k;while (scanf("%d%d%d", &N, &M, &k) != EOF){memset(w, 0x7f, sizeof(w));int ww;char s1[50];char s2[50];int acnt = 0;int bcnt = 0;int a, b;nodecnt = 0;root = NewNode();while (k--){scanf("%s%s%d", s1, s2, &ww);a = dic_insert(s1, acnt);b = dic_insert(s2, bcnt);w[a][b] = ww;}printf("%d/n", KM());}return 0;}