拓扑排序

代码

#include <stdio.h>
#include <stdlib.h>

#define N 100

int g[N][N];
int time[N];
int maxtime[N];
int indegree[N];

typedef struct node {
    int val;
    node* next;
}*grapgnode;

typedef struct graph {
    int size;
    grapgnode* list;
}*G;

int max(int a, int b) {
    if (a > b) {
        return a;
    }
    else {
        return b;
    }
}

int main()
{
    /********** Begin **********/
    int n;
    printf("请输入课程的个数：");
    scanf("%d", &n);
    for (int i = 1; i <= n; i++) {
        printf("请输入第%d门课程的课程时间：",i);
        scanf("%d", &time[i]);
    }
    //构建邻接表
    G g = (G)malloc(sizeof(graph));
    g->size = n;
    g->list = (grapgnode*)malloc(n * sizeof(node) + 1);
    for (int i = 1; i <= n; i++) {
        g->list[i] = (grapgnode)malloc(sizeof(node));
        g->list[i]->next = NULL;
    }
    //初始化入度数组 并赋值
    printf("请输入A门课程要在B门之前开课,输入-1 -1结束\n");
    int u, v;
    while (1) {
        printf("A B:");
        scanf("%d%d", &u, &v);
        if (u == -1 && v == -1) {
            break;
        }
        indegree[v]++;
        grapgnode node = (grapgnode)malloc(sizeof(node));
        node->val = v;
        node->next = g->list[u]->next;
        g->list[u]->next = node;
    }
    int target;
    printf("查询编号为几的课程的最小开启时间：");
    scanf("%d", &target);
    //用队列保存入度为0的点
    int que[1000];
    int head = 0, tail = 0;
    for (int i = 1; i <= n; i++) {
        if (indegree[i] == 0) {
            que[tail++] = i;
            if (i == target) {
                goto found;
            }
        }
    }
    while (head < tail) {
        int cur = que[head];
        grapgnode curnode = g->list[cur]->next;
        while (curnode) {
            indegree[curnode->val]--;
            maxtime[curnode->val] = max(maxtime[cur] + time[cur],maxtime[curnode->val]);
            if (indegree[curnode->val] == 0) {
                que[tail++] = curnode->val;
            }
            curnode = curnode->next;
        }
        head++;
    }
    goto found;
    //
    /********** End **********/
    return 0;

found:
    printf("最小时间为：%d", maxtime[target]);
    return 0;
}