BZOJ 2662

#include<bits/stdc++.h>
using namespace std;
const int maxn = 10000;
const int maxxn = 55;
#define inf 0x3f3f3f
queue <int > q;
 
int n,m,k,tot = 0;
int ans = 21474340;
int e[maxxn][maxxn];
int head[maxxn];
int v[maxxn][maxxn];
int d[maxxn][maxxn];
struct node {
    int fr,ver,value,Next;
};
node edge[maxn];
 
inline void add (int x,int y,int z)  {
    edge[++tot].fr = x; edge[tot].ver = y; edge[tot].value = z; edge[tot].Next = head[x]; head[x] = tot;
}
inline int Read () {
    int xx = 0;
    int ff = 1;
    char ch = getchar();
    while (ch < '0'||ch > '9') {
        if (ch == '-') ff = -1;
        ch = getchar();
    }
    while (ch >= '0'&&ch <= '9') {
        xx = (xx << 1) + (xx << 3) + ch - '0';
        ch = getchar();
    }
    return xx * ff;
}
void spfa() {
	d[1][0] = 0;
	q.push(1);
	q.push(0);
	v[1][0] = 1;
	while (!q.empty()) {
		int x = q.front();
		q.pop();
		int zz = q.front();
		q.pop();
		v[x][zz] = 0;
		for (int i = head[x];i;i = edge[i].Next) {
			int y = edge[i].ver; int z = edge[i].value;
			if (d[y][zz] > d[x][zz] + z) {
				d[y][zz] = d[x][zz] + z;
				if (v[y][zz] == 0) {
					q.push(y); 
					q.push(zz);
					v[y][zz] = 1;
				}
			}
			if ((e[x][y] != -1)&&(d[x][zz] + e[x][y]/2 <d[y][zz+ 1])&&(zz < k)) {
				d[y][zz + 1] = d[x][zz] + e[x][y]/2;
				if (v[y][zz + 1] == 0) q.push(y),q.push(zz + 1),v[y][zz + 1] = 1;
			}
		}
	}
}
 
 
int main () {
    n = Read(); m = Read(); k = Read();
    memset(e,-1,sizeof(e));
    for (int i = 1;i <= m;i++) {
        int a = Read(); int b = Read(); int c = Read();
        e[a][b] = c;
        e[b][a] = c;
        add(a,b,c); add(b,a,c);
    }
    memset(v,0,sizeof(v));
    memset(d,inf,sizeof(d));
    spfa();
    for (int i = 0;i <= k;i++) {
        ans = min(ans,d[n][i]);
    }
    printf("%d\n",ans);
    return 0;
}