HDU 2255 ——奔小康赚大钱——————【KM算法裸题】

#include<stdio.h>
#include<algorithm>
#include<string.h>
#include<vector>
using namespace std;
const int maxn = 550;
const int INF = 0x3f3f3f3f;
int nx, ny, lx[maxn], ly[maxn];
bool visx[maxn], visy[maxn];
int linker[maxn], slack[maxn];
int G[maxn][maxn];
bool dfs(int x){
    visx[x] = 1;                    //标记X的匈牙利树节点
    for(int y = 1; y <= ny; y++){
        if(visy[y]) continue;
        int tmp = lx[x] + ly[y] - G[x][y];
        if(tmp == 0){   //找到了一条可以加入相等子图的新边
            visy[y] = 1;    //标记Y的匈牙利树节点
            if(linker[y] == -1 || dfs(linker[y])){  //找到了增广路
                linker[y] = x;
                return true;
            }
        }else if(slack[y] > tmp){       //更新松弛量
            slack[y] = tmp;
        }
    }
    return false;
}
int KM(){
    memset(linker,-1,sizeof(linker));   //匹配数组
    memset(ly,0,sizeof(ly));            //初始化Y节点顶标
    for(int i = 1; i <= nx; i++){
        lx[i] = -INF;
        for(int j = 1; j <= ny; j++){
            if(lx[i] < G[i][j]){
                lx[i] = G[i][j];        //初始化X节点顶标
            }
        }
    }
    for(int x = 1; x <= nx; x++){       //找每个X的增广路
        for(int i = 1; i <= ny; i++){   //初始化松弛量
            slack[i] = INF;
        }
        while(true){
            memset(visx,0,sizeof(visx));
            memset(visy,0,sizeof(visy));
            if(dfs(x)) break;               //找到了增广路
            int d = INF;
            for(int i = 1; i <= ny; i++){
                if(!visy[i] && d > slack[i]){   //Yi不在匈牙利树(交错树)中
                    d = slack[i];
                }
            }
            for(int i = 1; i <= nx; i++){       //Xi在匈牙利树中，更新顶标
                if(visx[i]){
                    lx[i] -= d;
                }
            }
            for(int i = 1; i <= ny; i++){
                if(visy[i]){                //Yi在匈牙利树中，更新顶标
                    ly[i] += d;
                }else{                      //更新松弛量
                    slack[i] -= d;
                }
            }
        }
    }
    int ret = 0;
    for(int i = 1; i <= ny; i++){          //求和
        if(linker[i] != -1){
            ret += G[linker[i]][i];
        }
    }
    return ret;
}
int main(){
    int n;
    while(scanf("%d",&n)!=EOF){
        memset(G,0,sizeof(G));
        int c;
        for(int i = 1; i <= n; i++){
            for(int j = 1; j <= n; j++){
                scanf("%d",&c);
                G[i][j] = c;
            }
        }
        nx = ny = n;
        int res = KM();
        printf("%d\n",res);
    }
    return 0;
}