Java 100% Time & 100% Space
```\npublic String destCity(List> paths) {\n        Map cityToCityMap = new HashMap<>();\n        \n        for (List pathDuo : paths) {\n            cityToCity
```\npublic String destCity(List<List<String>> paths) {\n        Map<String, String> cityToCityMap = new HashMap<>();\n        \n        for (List<String> pathDuo : paths) {\n            cityToCityMap.put(pathDuo.get(0), pathDuo.get(1));\n        }\n        \n        for (String path : cityToCityMap.values()) {\n            if (cityToCityMap.get(path) == null) {\n                return path;\n            }\n        }\n        \n        return null;\n    }
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