• luogu P4779 【模板】单源最短路径(标准版)


    线段树优化dij
    哈哈哈哈哈哈哈哈哈哈哈哈哈哈哈哈
    我可能是个智障

    // luogu-judger-enable-o2
    #pragma GCC diagnostic error "-std=c++11"
    #pragma GCC optimize("-fdelete-null-pointer-checks,inline-functions-called-once,-funsafe-loop-optimizations,-fexpensive-optimizations,-foptimize-sibling-calls,-ftree-switch-conversion,-finline-small-functions,inline-small-functions,-frerun-cse-after-loop,-fhoist-adjacent-loads,-findirect-inlining,-freorder-functions,no-stack-protector,-fpartial-inlining,-fsched-interblock,-fcse-follow-jumps,-fcse-skip-blocks,-falign-functions,-fstrict-overflow,-fstrict-aliasing,-fschedule-insns2,-ftree-tail-merge,inline-functions,-fschedule-insns,-freorder-blocks,-fwhole-program,-funroll-loops,-fthread-jumps,-fcrossjumping,-fcaller-saves,-fdevirtualize,-falign-labels,-falign-loops,-falign-jumps,unroll-loops,-fsched-spec,-ffast-math,Ofast,inline,-fgcse,-fgcse-lm,-fipa-sra,-ftree-pre,-ftree-vrp,-fpeephole2",3)
    #pragma GCC target("avx","sse2")
    #include<cstdio>
    #include<cstring>
    #include<algorithm> 
    using namespace std;
    const int maxn =200007;
    const int maxm = 500007;
    const int INF = 0x7fffffff;
    int n,m;
    inline int read() {
        int x=0;
        char c=getchar();
        while(c<'0'||c>'9') 
            c=getchar();
        while(c>='0'&&c<='9') x=x*10+c-'0',c=getchar();
        return x;
    }
    struct node{
        int v,next,w;
    }edge[maxm];
    int num=0,head[maxn];
    inline void add_edge(int a,int b,int c) {
        edge[++num].v=b;edge[num].w=c;edge[num].next=head[a];head[a]=num;
    } 
    int dis[maxn],ans[maxn],s,t;
    int tree[maxn<<2],leaf;
    inline int check(int i,int j) {
        return dis[i]<dis[j]?i:j;
     } 
    inline void build() {
        std::memset(dis,0x3f,sizeof dis);// for(int i=0;i<=n+1;i++) dis[i]=INF;
        for(leaf=1;leaf<=n;leaf<<=1);--leaf;
        for(int i=1;i<=n;++i)tree[leaf+i]=i;
    }
    inline void modify(int x,int y) {
        dis[x]=y,x+=leaf,x>>=1;
        while(x) tree[x]=check(tree[x<<1],tree[x<<1|1]),x=x>>1;
    }
    void dijkstra(int s) {
        build();
        dis[s]=0;
        int u=s;
        for(int i=1;i<=n;++i) {
        	ans[u]=dis[u];
            const int disu=dis[u];
        	modify(u,INF); 
        	for(int j=head[u];j;j=edge[j].next){
          		int v=edge[j].v;
          		if(dis[v]<INF&&dis[v]>disu+edge[j].w)
            		modify(v,disu+edge[j].w);
        	}
        	u=tree[1];
      	}
    }
    int main() {
        int k;
        n=read(),m=read(),k=read();
        for(int a,b,c,i=1;i<=m;++i) {
            a=read(),b=read(),c=read();
            add_edge(a,b,c);
        }
        dijkstra(k);
        for(int i=1;i<=n;++i) {
        	if(dis[i]==0x3f3f3f3f)ans[i]=INF;
            printf("%d ",ans[i]);
        }
        return 0;
    }
    
    
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  • 原文地址:https://www.cnblogs.com/sssy/p/9363978.html
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