HDU - 2544 - 最短路

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HDU - 2544 - 最短路

Dijkstra最短路算法

题目

hdu 2544

解法

依旧是用的Dijkstra的模版，不过刚开始Wa了，应该是数组开小了吧。

// 2544 - 最短路const int INF = 0x3f3f3f3f;const int maxn = 105;int N, M;int road[maxn][maxn];int d[maxn] = {INF};bool used[maxn];void dijkstra() {    fill(d, d + N, INF);    fill(used, used + N, false);    d[1] = 0;    for (; ; ) {        int v = -1;        for (int u = 1; u <= N; u++) {            if (!used[u] && (v == -1 || d[u] < d[v])) {                v = u;            }        }        if (v == -1) {            break;        }        used[v] = true;        for (int u = 1; u <= N; u++) {            d[u] = min(d[u], d[v] + road[v][u]);        }    }}void solve() {    dijkstra();    printf("%d\n", d[N]);}int main() {    int A, B, C;    while (~scanf("%d%d", &N, &M)) {        if (N == 0 && M == 0) {            break;        }        for (int i = 1; i <= N; i++) {            for (int j = 1; j <= i; j++) {                road[i][j] = road[j][i] = INF;            }        }        while (M--) {            scanf("%d%d%d", &A, &B, &C);            road[A][B] = road[B][A] = C;        }        solve();    }    return 0;}

Ac代码

// 2544 - 最短路// Dijkstraconst int INF = 0x3f3f3f3f;const int maxn = 1001;int edge[maxn][maxn];int d[maxn];bool used[maxn];int N, M;void dijkstra() {    fill(d, d + maxn, INF);    fill(used, used + maxn, false);    d[1] = 0;    for (; ; ) {        int v = -1;        for (int u = 1; u <= N; u++) {            if (!used[u] && (v == -1 || d[u] < d[v])) {                v = u;            }        }        if (v == -1) {            break;        }        used[v] = true;        for (int u = 1; u <= N; u++) {            d[u] = min(d[u], d[v] + edge[v][u]);        }    }}int main() {    int from, to, cost;    while (~scanf("%d%d", &N, &M)) {        if (N == 0 && M == 0) {            break;        } else {            for (int i = 1; i <= N; i++) {                for (int j = 1; j < i; j++) {                    edge[i][j] = edge[j][i] = INF;                }            }            for (int i = 1; i <= N; i++) {                edge[i][i] = 0;            }            while (M--) {                scanf("%d%d%d", &from, &to, &cost);                if (cost < edge[from][to]) {                    edge[from][to] = edge[to][from] = cost;                }            }            dijkstra();            printf("%d\n", d[N]);        }    }    return 0;}

总结

现在对数组范围大小还是没有一个清晰的概念，，，或许题做多了就知道了吧。。

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