（为了防止有人掰扯我，这里只放出部分代码） 你见过谁家的dp，一：可以正着枚举k

 for (int k = 1; k <= n; k++) {
        for (int i = 1; i <= n; i++) {
            for (int j = 1; j <= n; j++) {
                if (mp[i][k] + mp[k][j] < mp[i][j]) {
                    mp[i][j] = mp[i][k] + mp[k][j];
                }
            }
        }
    }

二：可以倒着枚举k

for (int k = n; k >= 1; k--) {
        for (int i = 1; i <= n; i++) {
            for (int j = 1; j <= n; j++) {
                if (mp[i][k] + mp[k][j] < mp[i][j]) {
                    mp[i][j] = mp[i][k] + mp[k][j];
                }
            }
        }
    }

三：我甚至可以先枚举奇数的k，在枚举偶数的k

 for (int k = 1; k <= n; k += 2) {
        for (int i = 1; i <= n; i++) {
            for (int j = 1; j <= n; j++) {
                if (mp[i][k] + mp[k][j] < mp[i][j]) {
                    mp[i][j] = mp[i][k] + mp[k][j];
                }
            }
        }
    }
    for (int k = 2; k <= n; k += 2) {
        for (int i = 1; i <= n; i++) {
            for (int j = 1; j <= n; j++) {
                if (mp[i][k] + mp[k][j] < mp[i][j]) {
                    mp[i][j] = mp[i][k] + mp[k][j];
                }
            }
        }
    }