uva 10330 - Power Transmission
题目大意:最大流问题。
解题思路:増广路算法。
#include <stdio.h> #include <string.h> #include <queue> using namespace std; #define min(a,b) (a)<(b)?(a):(b) const int N = 105; const int INF = 0x3f3f3f3f; int n, s[N], g[N][N], f[N][N]; void init() { memset(s, 0, sizeof(s)); memset(g, INF, sizeof(g)); memset(f, INF, sizeof(f)); for (int i = 1; i <= n; i++) scanf("%d", &s[i]); int a, b, c, t; scanf("%d", &t); for (int i = 0; i < t; i++) { scanf("%d%d%d", &a, &b, &c); g[a][b] = min(g[a][b], c); f[a][b] = 0; } scanf("%d%d", &a, &b); for (int i = 0; i < a; i++) { scanf("%d", &c); g[0][c]--; f[0][c] = 0; } for (int i = 0; i < b; i++) { scanf("%d", &c); g[c][n + 1]--; f[c][n + 1] = 0; } } int solve() { n++; s[n] = INF; int a[N], vis[N]; int ans = 0; queue<int> q; while (1) { memset(vis, 0, sizeof(vis)); memset(a, 0, sizeof(a)); int c = 0, t; vis[c] = 0; a[c] = INF; q.push(c); while (!q.empty()) { c = q.front(), q.pop(); for (int i = 1; i <= n; i++) { if (g[c][i] == INF) continue; t = min(g[c][i] - f[c][i], min(a[c], s[i])); if (t > a[i]) { vis[i] = c; a[i] = t; q.push(i); } } } if (a[n] == 0) break; ans += a[n]; for (int i = n; i; i = vis[i]) { s[i] -= a[n]; f[vis[i]][i] += a[n]; } } return ans; } int main () { while (scanf("%d", &n) == 1) { init(); printf("%d\n", solve()); } return 0; }