Poj 2391 ombrophobic bovines [simple network stream]

... The first question about network flow

Create a chart with a template

# Include <cstdio> # include <cstdlib> # include <iostream> # include <algorithm> # include <cstring> # include <cmath> # include <vector> using namespace STD; long long F, P; long cowsum; const int max = 555; long tttt = (1 <31)-1; const long INF = tttt * tttt; long long dis [Max] [Max]; long cownum [Max]; long sheld [Max]; // sap maximum flow template const long maxn = 1111; // maximum number of points const long maxm = 222222; // maximum number of edges struc T node {long from, to, next; long cap;} edge [maxm]; long tol; long head [maxn]; long Dep [maxn]; long long gap [maxn]; // gap [x] = Y: indicates that the number of Dep [I] = X in the residual network is ylong long N; // n is the total number of points, including the source and sink void Init () {Tol = 0; memset (Head,-1, sizeof (head ));} void addedge (Long U, long V, long w) {edge [tol]. from = u; edge [tol]. to = V; edge [tol]. CAP = W; edge [tol]. next = head [u]; head [u] = tol ++; edge [tol]. fro M = V; edge [tol]. to = u; edge [tol]. CAP = 0; edge [tol]. next = head [v]; head [v] = tol ++;} void BFS (long start, long end) {memset (DEP,-1, sizeof (DEP); memset (GAP, 0, sizeof (GAP); Gap [0] = 1; long que [maxn]; long front, rear; front = rear = 0; Dep [end] = 0; que [rear ++] = end; while (front! = Rear) {long u = que [Front ++]; If (front = maxn) Front = 0; For (long I = head [u]; I! =-1; I = edge [I]. Next) {long v = edge [I]. To; If (DEP [v]! =-1) continue; que [rear ++] = V; If (Rear = maxn) rear = 0; Dep [v] = Dep [u] + 1; ++ gap [Dep [v] ;}} long SAP (long start, long end) {long res = 0; BFS (START, end ); long long cur [maxn]; long s [maxn]; long top = 0; memcpy (cur, Head, sizeof (head); long u = start; long long I; while (DEP [start] <n) {If (u = END) {long temp = inf; long inser; for (I = 0; I <top; I ++) if (temp> edge [s [I]. CAP) {Temp = edge [s [I]. CAP; inser = I ;}for (I = 0; I <top; I ++) {edge [s [I]. cap-= temp; edge [s [I] ^ 1]. cap + = temp;} res + = temp; Top = inser; u = edge [s [Top]. from;} If (u! = End & gap [Dep [u]-1] = 0) // when a fault occurs, the break is not added. For (I = cur [u]; I! =-1; I = edge [I]. Next) if (edge [I]. Cap! = 0 & Dep [u] = Dep [edge [I]. To] + 1) break; if (I! =-1) {cur [u] = I; s [top ++] = I; u = edge [I]. to;} else {long min = N; for (I = head [u]; I! =-1; I = edge [I]. next) {If (edge [I]. CAP = 0) continue; If (min> Dep [edge [I]. to]) {min = Dep [edge [I]. to]; cur [u] = I ;}-- gap [Dep [u]; Dep [u] = min + 1; ++ gap [Dep [u]; if (u! = Start) u = edge [s [-- top]. from ;}} return res;} void input () {scanf ("% LLD", & F, & P); n = f * 2 + 2; for (long I = 1; I <= f; I ++) {for (long j = 1; j <= f; j ++) {dis [I] [J] = inf;} dis [I] [I] = 0;} For (long I = 1; I <= f; I ++) {long a, B; scanf ("% LLD", & A, & B); cownum [I] = A; sheld [I] = B; cowsum + = A;} For (long I = 1; I <= P; I ++) {long U, V, Len; scanf ("% LLD", & U, & V, & Len); If (DIS [u] [v]> Len) {dis [v] [u] = dis [u] [v] = Len ;}} void Floyd () {for (long k = 1; k <= F; k ++) {for (long I = 1; I <= f; I ++) {for (long j = 1; j <= f; j ++) {If (DIS [I] [J]> dis [I] [k] + dis [k] [J]) dis [I] [J] = dis [I] [k] + dis [k] [J] ;}}} void makemap (long maxedge) {for (long I = 1; I <= f; I ++) {for (long j = 1; j <= f; j ++) {If (DIS [I] [J] <= maxedge) {addedge (I, j + F, INF) ;}}for (long I = 1; I <= f; I ++) {addedge (0, I, cownum [I]);} For (long I = 1; I <= f; I ++) {addedge (I + F, 2 * F + 1, sheld [I]) ;}} int main () {# ifndef online_judgefreopen ("G:/1.txt"," r ", stdin); freopen ("G:/2.txt"," W ", stdout); # endifinput (); Floyd (); long ans; long l = 0, r = 0, mid = 0; For (long I = 1; I <= f; I ++) {for (long j = 1; j <= F; j ++) {If (DIS [I] [J] <inf) r = max (R, DIS [I] [J]) ;}} R + = 10; mid = (L + r)> 1; long ans =-1; while (L <r) {Init (); makemap (MID ); ans = SAP (* F + 1); If (ANS> = cowsum) {ans = r = mid; Mid = (L + r)> 1 ;} else {L = Mid + 1; Mid = (L + r)> 1 ;}} printf ("% LLD \ n", ANS );}